Transition Metal Complexes Coordinated by Water

molecules Article

Transition Metal Complexes Coordinated by Water Soluble Phosphane Ligands: How Cyclodextrins Can Alter the Coordination Sphere? Michel Ferreira, Hervé Bricout, Sébastien Tilloy and Eric Monflier * University of Artois, CNRS, Centrale Lille, ENSCL, University of Lille, UMR 8181, Unité de Catalyse et de Chimie du Solide (UCCS), F-62300 Lens, France; [email protected] (M.F.); [email protected] (H.B.); [email protected] (S.T.) * Correspondence: [email protected]; Tel.: +33-321-791-772; Fax: +33-321-791-717 Academic Editor: Bernard Martel Received: 9 December 2016; Accepted: 12 January 2017; Published: 17 January 2017

Abstract: The behaviour of platinum(II) and palladium(0) complexes coordinated by various hydrosoluble monodentate phosphane ligands has been investigated by 31 P{1 H} NMR spectroscopy in the presence of randomly methylated β-cyclodextrin (RAME-β-CD). This molecular receptor can have no impact on the organometallic complexes, induce the formation of phosphane low-coordinated complexes or form coordination second sphere species. These three behaviours are under thermodynamic control and are governed not only by the affinity of RAME-β-CD for the phosphane but also by the phosphane stereoelectronic properties. When observed, the low-coordinated complexes may be formed either via a preliminary decoordination of the phosphane followed by a complexation of the free ligand by the CD or via the generation of organometallic species complexed by CD which then lead to expulsion of ligands to decrease their internal steric hindrance. Keywords: platinum; palladium; TPPTS; cyclodextrin; hydrosoluble organometallic complexes; supramolecular chemistry

1. Introduction Biphasic aqueous organometallic catalysis is one of the greenest solutions to produce organic chemicals [1,2]. Indeed, water is not only cheap and non-toxic, but also permits one to immobilize the catalyst in an aqueous phase by the use of water-soluble ligands, leading to ease of recycling by simple decantation at the end of the reaction [3]. The most widespread ligand used in such systems is TPPTS (tris(3-sulfonatophenyl)phosphane sodium salt, Table 1, entry 1) which is responsible for the industrial success of the aqueous biphasic propene hydroformylation (Ruhrchemie-Rhône Poulenc process, 1984) [4]. Attractive for partially water-soluble olefins, this strategy suffers from low catalytic activity when hydrophobic substrates are used due to mass transfer limitations. The alternative approaches to overcome this drawback have been recently reviewed [5,6]. These include the use of cyclodextrins (CDs) which are widely recognized as outstanding water-soluble receptors in aqueous biphasic organometallic processes [7]. These macrocycles were firstly used as phase transfer agents between the organic and the aqueous layers by forming inclusion complexes with a hydrophobic substrate at the interface in order to convert it thanks to a water-soluble organometallic catalyst. However, CDs are more than simple receptors for hydrophobic substrates and can be now considered as polyfunctional entities in aqueous biphasic organometallic catalysis [8]. In particular, CDs can modify the catalytic species involved in the reaction. As an example, when TPPTS is combined with a rhodium precursor to catalyse the 1-decene aqueous biphasic hydroformylation reaction, a linear to branched aldehyde ratio drop is

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Molecules 2017,the 22, 140 2 of 25 observed when experiment is conducted in the presence of RAME-β-CD (=randomly methylated β-CD) [9]. Under CO/H2 pressure and with RAME-β-CD, equilibria displacements between the CD) [9]. Under CO/H2 pressure and with RAME-β-CD, equilibria displacements between the different different catalytic species towards the formation of phosphane low-coordinated species are observed. catalytic species towards the formation of phosphane low-coordinated species are observed. These Theseequilibria, equilibria, displaced by TPPTS inclusion into the CD cavity, are responsible for the drop in displaced by TPPTS inclusion into the CD cavity, are responsible for the drop in regioselectivity regioselectivity (Scheme 1) [10]. (Scheme 1) [10].

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CD) [9]. Under CO/H222 pressure and with RAME-β-CD, equilibria displacements between the different CD) CO/H22 pressure and RAME-β-CD, equilibria displacements between the CD) [9]. [9]. Under Under pressure and with with of RAME-β-CD, displacements the different different catalytic speciesCO/H towards the formation phosphane equilibria low-coordinated species between are observed. These catalytic species towards the formation of phosphane low-coordinated species are observed. These Schemespecies 1. Equilibria between the different catalytic species duringspecies 1-decene aqueous biphasic catalytic towards the formation of phosphane low-coordinated are observed. These equilibria, displaced bybetween TPPTS inclusion into the CD cavity, are responsible for the drop in regioselectivity Scheme 1. Equilibria the different catalytic species during 1-decene aqueous biphasic equilibria, displaced by TPPTS inclusion into the CD cavity, are responsible for the drop in regioselectivity hydroformylation assisted by RAME-β-CD. equilibria, displaced by TPPTS inclusion into the CD cavity, are responsible for the drop in regioselectivity (Scheme 1) [10]. hydroformylation assisted by RAME-β-CD. (Scheme 1) [10]. (Scheme 1) [10].

Along the same lines, when a water-soluble triphenylphosphane derivative possessing a higher affinity the towards is when involved in a rhodium HRhCOL 3 type species derivative (L = p-tBuPhP(m-PhSO 2 Along sameCDs lines, a water-soluble triphenylphosphane possessing3Na) a higher phosphane), unsaturated catalytic species are also formed in the presence of CD even when the affinity towards CDs is involved in a rhodium HRhCOL3 type species (L = p-tBuPhP(m-PhSO3 Na)2 organometallic complex was not exposed to aare CO/H 2 atmosphere [11]. phosphane), unsaturated catalytic species also formed in the presence of CD even when the organometallic complex was not exposed to a CO/H atmosphere [11]. Table 1. Structure, abbreviation of the water-soluble 2phosphanes used, and value of the association constant (K) for the inclusion complexes between the RAME-β-CD and This behaviour, not observed with TPPTS, was attributedthetophosphane. the more stable inclusion complex formed between the CD and the phosphane, due to the presence of the well-recognized Entry Structure Name Abbreviation K (M−1) a,b p-tert-butylphenyl group. Moreover, it has been demonstrated that the combination of the same tris(3-sodium-sulfonatophenyl)phosphane [15]is to say 1 ligand with another metal centre, e.g., palladium or platinum, TPPTS led to the same behaviour,840 that formation of low-coordinated organometallic species [12]. Scheme Equilibria between different catalytic specieswith during 1-decene aqueous triphenylphosphane biphasic tris(4-methyl-3-sodium-sulfonatophenyl)phosphane However, the 1. combination of athe palladium precursor a water-soluble Scheme between the 2 Scheme 1. 1. Equilibria Equilibria between the different different catalytic catalytic species species during during 1-decene 1-decene aqueous aqueous biphasic biphasic 960 [15] hydroformylation assisted by RAME-β-CD. tris(p-Me)TPPTS hydroformylation assisted by RAME-β-CD. derivative possessing a p-tert-butylbiphenyl hydroformylation assisted by RAME-β-CD. group led to the formation of a stable second-sphere coordinationAlong adduct where thewhen CD encapsulated the ligand directly bounded to the ametal the same lines, a water-soluble triphenylphosphane derivative possessing highercentre [13]. tris(4-methoxy-3-sodium-sulfonatophenyl)phosphane Along the same lines, when aa water-soluble triphenylphosphane derivative possessing aa higher Along the same lines, when water-soluble triphenylphosphane derivative possessing 3 0 [15] affinity towards CDs is in HRhCOL type species (L 33Na)22 Such species already observed with a phosphane bearing groupshigher [14]. affinityhad towards CDs been is involved involved in aa rhodium rhodium HRhCOL3333 tris(p-OMe)TPPTS type species adamantyl (L == p-tBuPhP(m-PhSO p-tBuPhP(m-PhSO 33Na)22 affinity towards CDs is involved a rhodium HRhCOL 3 type species (L = p-tBuPhP(m-PhSO3Na)2 phosphane), unsaturated catalytic inspecies are also formed in the presence of CD even when the phosphane), unsaturated catalytic species are also formed in phosphane), unsaturated catalytic species are also formed in the the presence presence of of CD CD even even when when the the organometallic complex was not exposed to a CO/H 22 atmosphere [11]. tris(6-methyl-3-sodium-sulfonatophenyl)phosphane Table 1. Structure, abbreviation of the water-soluble phosphanes used, and value of the association organometallic complex was not exposed to a CO/H 22 atmosphere [11]. organometallic complex was not exposed to a CO/H2 atmosphere [11]. 0 [15] 4 tris(o-Me)TPPTS 1. Structure, abbreviation of the water-soluble used, and and value of the association constantTable (K) for the inclusion complexes between thephosphanes RAME-β-CD the phosphane. Table 1. Structure, abbreviation of the water-soluble phosphanes used, and value of the association

Table 1. Structure, of the water-soluble phosphanes used, andphosphane. value of the association constant (K) for the abbreviation inclusion complexes between the RAME-β-CD and the constant constant (K) (K) for for the the inclusion inclusion complexes complexes between between the the RAME-β-CD RAME-β-CD and and the the phosphane. phosphane. −1 ) a,b tris(6-methoxy-3-sodium-sulfonatophenyl)phosphane Entry Structure Name Abbreviation a,b K−1 −1)(M a,b Structure Name K −1 a,b 5 Entry 0 [15] Entry Structure Name Abbreviation Abbreviation K (M (M−1 ) a,b Entry Structure Name Abbreviation K (M−1) a,b tris(o-OMe)TPPTS tris(3-sodium-sulfonatophenyl)phosphane tris(3-sodium-sulfonatophenyl)phosphane tris(3-sodium-sulfonatophenyl)phosphane 1 11 840 [15] 840 tris(3-sodium-sulfonatophenyl)phosphane 840 [15] [15] TPPTS TPPTS 840 [15] 1 TPPTS TPPTS trisulfonated monobiphenyldiphenylphosphane 6 9900 c P(Biph)Ph2TS tris(4-methyl-3-sodium-sulfonatophenyl)phosphane tris(4-methyl-3-sodium-sulfonatophenyl)phosphane tris(4-methyl-3-sodium-sulfonatophenyl)phosphane 960 [15] 2 22 960 [15] tris(4-methyl-3-sodium-sulfonatophenyl)phosphane 960 tris(p-Me)TPPTS tris(p-Me)TPPTS 2 960 [15] [15] tris(p-Me)TPPTS tris(p-Me)TPPTS

7 3 33 3

8 4 4 44 a

trisulfonated bisbiphenylmonophenylphosphane

tris(4-methoxy-3-sodium-sulfonatophenyl)phosphane >100,000 c tris(4-methoxy-3-sodium-sulfonatophenyl)phosphane tris(4-methoxy-3-sodium-sulfonatophenyl)phosphane 00 [15] P(Biph)2PhTS tris(4-methoxy-3-sodium-sulfonatophenyl)phosphane [15] 0 [15] tris(p-OMe)TPPTS 0 [15] tris(p-OMe)TPPTS tris(p-OMe)TPPTS tris(p-OMe)TPPTS

trisulfonated trisbiphenylphosphane

>100,000 c tris(6-methyl-3-sodium-sulfonatophenyl)phosphane tris(6-methyl-3-sodium-sulfonatophenyl)phosphane 0 [15] P(Biph)3TS tris(6-methyl-3-sodium-sulfonatophenyl)phosphane tris(6-methyl-3-sodium-sulfonatophenyl)phosphane 00 [15] tris(o-Me)TPPTS [15] 0 [15] tris(o-Me)TPPTS tris(o-Me)TPPTS In each case, the stoichiometry has been determined totris(o-Me)TPPTS be equal to 1:1 when an inclusion complex

due to the random methylation of the CD; c association was formed; b K constant is an average constant tris(6-methoxy-3-sodium-sulfonatophenyl)phosphane tris(6-methoxy-3-sodium-sulfonatophenyl)phosphane 55 00 [15] tris(6-methoxy-3-sodium-sulfonatophenyl)phosphane tris(6-methoxy-3-sodium-sulfonatophenyl)phosphane [15] tris(o-OMe)TPPTS determined between native β-CD and the phosphane. 5 0 [15] 0 [15] 5constant tris(o-OMe)TPPTS tris(o-OMe)TPPTS tris(o-OMe)TPPTS

6 66

trisulfonated monobiphenyldiphenylphosphane trisulfonated trisulfonated monobiphenyldiphenylphosphane monobiphenyldiphenylphosphane P(Biph)Ph222TS P(Biph)Ph P(Biph)Ph22TS TS

9900 cccc 9900 9900 c

7 77

trisulfonated bisbiphenylmonophenylphosphane trisulfonated trisulfonated bisbiphenylmonophenylphosphane bisbiphenylmonophenylphosphane P(Biph)222PhTS P(Biph) P(Biph)22PhTS PhTS

>100,000 cccc >100,000 >100,000 c

8 88

trisulfonated trisbiphenylphosphane trisulfonated trisbiphenylphosphane trisulfonatedP(Biph) trisbiphenylphosphane 3TS P(Biph)333TS

>100,000 cccc >100,000 >100,000 c

22

tris(4-methyl-3-sodium-sulfonatophenyl)phosphane tris(4-methyl-3-sodium-sulfonatophenyl)phosphane tris(p-Me)TPPTS tris(p-Me)TPPTS

960 [15] [15] 960

33

tris(4-methoxy-3-sodium-sulfonatophenyl)phosphane tris(4-methoxy-3-sodium-sulfonatophenyl)phosphane tris(p-OMe)TPPTS tris(p-OMe)TPPTS

[15] 00 [15]

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tris(6-methyl-3-sodium-sulfonatophenyl)phosphane tris(6-methyl-3-sodium-sulfonatophenyl)phosphane tris(o-Me)TPPTS tris(o-Me)TPPTS

55

tris(6-methoxy-3-sodium-sulfonatophenyl)phosphane tris(6-methoxy-3-sodium-sulfonatophenyl)phosphane tris(o-OMe)TPPTS tris(o-OMe)TPPTS Name Abbreviation

[15] 00 [15]

Table 1. Cont. Entry

Structure

[15] 00 [15]

K (M−1 ) a,b

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trisulfonated monobiphenyldiphenylphosphane trisulfonatedmonobiphenyldiphenylphosphane monobiphenyldiphenylphosphane trisulfonated P(Biph)Ph P(Biph)Ph 2TS 2 TS P(Biph)Ph 2TS

7 77

trisulfonated bisbiphenylmonophenylphosphane trisulfonatedbisbiphenylmonophenylphosphane bisbiphenylmonophenylphosphane trisulfonated c c >100,000 c >100,000 >100,000 P(Biph) 2PhTS P(Biph) 2 PhTS P(Biph) 2PhTS trisulfonated trisbiphenylphosphane trisulfonated trisulfonatedtrisbiphenylphosphane trisbiphenylphosphane 3TS P(Biph) P(Biph) 3TS P(Biph) 3 TS

8 88 a

9900 cc9900 c 9900

c c >100,000 c >100,000 >100,000

In each case, the stoichiometry has been determined to be equal to 1:1 when an inclusion complex

Incase, eachthe case, the stoichiometry stoichiometry has determined been determined determined to be equal equal towhen 1:1 when when an inclusion inclusion complex a In each case, the has been be 1:1 an complex In each stoichiometry has been to beto equal to 1:1to an inclusion complex was formed; K constant constant is is an an average average constant constant due due to to the the random random methylation methylation of the the CD; CD; cc association association was formed; formed; bb K c of was K constant is an average constant due to the random methylation of the CD; association constant determined constant determined between native β-CD β-CD and and the the phosphane. phosphane. constant between native between nativedetermined β-CD and the phosphane. a

b

In order to get a better insight into the interaction phenomena between the CD and transition metal complexes, we want to show in this article how RAME-β-CD can interfere with different platinum(II) or palladium(0) complexes coordinated with various hydrosoluble ligands and how specific organometallic complexes can be obtained. These ligands include TPPTS itself but also TPPTS modified phosphanes containing substituents (methyl or methoxy groups) in ortho or para position and biphenyl modified phosphanes (Table 1). The interaction of the different phosphanes with RAME-β-CD has already been studied by our group [15], except for biphenylphosphane derivatives whose synthesis and catalytic properties have been exclusively published [16]. For each type of ligands, we have both examined the nature of the organometallic complex formed when mixing them with the metal precursor and the influence of the RAME-β-CD addition on these complexes. 2. Results and Discussion 2.1. Platinum Complexes The different complexes formed by mixing the K2 PtCl4 aqueous solution with 3 equiv. of phosphane were firstly analysed by 31 P{1 H} NMR. In a second step, RAME-β-CD has been added to the mixture in order to determine its influence on the coordination chemistry of the different ligands. 2.1.1. Complex Synthesis TPPTS Ligand As described in the literature [17], [Pt(TPPTS)3 Cl]Cl platinum complex is quantitatively synthetized by adding three equivalents of TPPTS to a K2 PtCl4 aqueous solution. As only one third of the platinum (195 Pt) has a spin of 1/2, the 31 P{1 H} NMR spectrum of this complex is characterized by a 1:4:1 triplet of doublets centred at δ = 24.5 ppm (1 JPcis –Pt = 2491 Hz; 2 JPcis –Ptrans = 19 Hz) corresponding to the two phosphorus atoms cis to the chloride and a 1:4:1 triplet of triplets centred at δ = 13.3 ppm (1 JPtrans –Pt = 3682 Hz; 2 JPcis –Ptrans = 19 Hz) corresponding to the phosphorus atom trans to the chloride (Figure 1). para-Substituted TPPTS Derivatives Similarly to TPPTS, [PtL3 Cl]Cl platinum complexes can be quantitatively synthetized by adding three equivalents of the para-substituted ligands tris(p-Me)TPPTS and tris(p-OMe)TPPTS to a solution of K2 PtCl4 (Figure 2). The two phosphorus atoms cis to the chloride appear respectively for [Pt(tris(p-Me)TPPTS)3 Cl]Cl and [Pt(tris(p-OMe)TPPTS)3 Cl]Cl at δ = 23.3 ppm (1 JPcis –Pt = 2488 Hz; 2 JP –P 1 2 31 1 cis trans = 19 Hz) and δ = 21.8 ppm ( JPcis –Pt = 2487 Hz; JPcis –Ptrans = 18 Hz) in their P{ H} NMR 1 spectra. The phosphorus atom trans to the chloride appears at δ = 11.5 ppm ( JPtrans –Pt = 3693 Hz; 2 JP –P 1 2 trans = 19 Hz) and δ = 9.8 ppm ( JPtrans –Pt = 3754 Hz; JPcis –Ptrans = 18 Hz). cis

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31 11 1H} NMR spectrum of [Pt(TPPTS)3Cl]Cl, [Pt] = 10 mM, 25 °C◦ in D2O. Figure 1. 31P{ Figure 1.1.31 H} NMR spectrum of [Pt(TPPTS)3Cl]Cl, Cl]Cl, [Pt] == 10 10 mM, mM, 25 25 °CCin inD D22O. O. Figure P{P{

= para-substituted phosphane

= para-substituted phosphane

phosphane oxide phosphane oxide

a)

a)

phosphane oxide

phosphane oxide

b)

b)

45

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(ppm) 31 P{1 H} NMR spectra of (a) [Pt(tris(p-Me)TPPTS) Cl]Cl and (b) [Pt(tris(p-OMe)TPPTS) Figure 2. 2. 31P{1H} NMR spectra of (a) [Pt(tris(p-Me)TPPTS)33 3 Cl]Cl, Figure Cl]Cl and (b) [Pt(tris(p-OMe)TPPTS)3Cl]Cl, ◦ [Pt][Pt] = 10 mM, 25 C in D O. 2 = 10 mM, 25 °C in D2O. Figure 2. 31P{1H} NMR spectra of (a) [Pt(tris(p-Me)TPPTS)3Cl]Cl and (b) [Pt(tris(p-OMe)TPPTS)3Cl]Cl, [Pt] = 10 mM, 25 °C in Derivatives DDerivatives 2O. ortho-Substituted TPPTS ortho-Substituted TPPTS

However, attempts tosynthetize synthetize[Pt(tris(o-Me)TPPTS) [Pt(tris(o-Me)TPPTS)33Cl]Cl 3Cl]Cl However, attempts Cl]Cl and and [Pt(tris(o-OMe)TPPTS) [Pt(tris(o-OMe)TPPTS) 3 Cl]Cl ortho-Substituted TPPTS to Derivatives were unsuccessful. Indeed, of three equivalents of ligand (towards platinum) to a K2PtCl were unsuccessful. Indeed,addition addition of three equivalents of ligand (towards platinum) to4 a However, attempts to synthetize [Pt(tris(o-Me)TPPTS)3Cl]Cl and [Pt(tris(o-OMe)TPPTS)3Cl]Cl were unsuccessful. Indeed, addition of three equivalents of ligand (towards platinum) to a K2PtCl4

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exclusively yields toyields formation of PtCl2Lof 2-type by a 1:4:1 triplet of Ksolution exclusively to formation PtClcomplex complex characterized by a 1:4:1 2 PtCl4 solution 2 L2 -typecharacterized doublets centredcentred at δ = at20.5 and and 24.524.5 ppm, respectively, forforPtCl 2(tris(o-Me)TPPTS) 2 and triplet of doublets δ = ppm 20.5 ppm ppm, respectively, PtCl (tris(o-Me)TPPTS) and 2 2 1H} 1 H} PtCl 2(tris(o-OMe)TPPTS)2.. As a consequence, free P{P{ PtCl free ligand ligand that that represents representsone onethird thirdof ofthe thetotal total3131 2 (tris(o-OMe)TPPTS) 2 1 1 NMRsurface surfacearea area is detected in in both cases, JP–Pt coupling constants (2750 (2750 and NMR detected(Figure (Figure3). 3).Moreover, Moreover, both cases, JP–Pt coupling constants 2590 Hz Hz for for PtCl 2(tris(o-OMe)TPPTS) 2 and PtCl 2PtCl (tris(o-Me)TPPTS) 2 respectively) are consistent with and 2590 PtCl (tris(o-OMe)TPPTS) and (tris(o-Me)TPPTS) respectively) are consistent 2 2 2 2 a trans coordination whenwhen compared with with cis-PtCl 2(TPPTS) 2 (1JP–Pt 1= 3720 Hz, Figure 4) and transwith a trans coordination compared cis-PtCl 2 (TPPTS)2 ( JP–Pt = 3720 Hz, Figure 4) and 1 = 2600 Hz) that have already been described [17]. The steric hindrance of these PtCl2(TPPTS) 2 (1JP–Pt trans-PtCl 2 (TPPTS)2 ( JP–Pt = 2600 Hz) that have already been described [17]. The steric hindrance of ligands, which havehave a higher cone angle than their is isobviously these ligands, which a higher cone angle than theirpara-substituted para-substitutedcounterparts, counterparts, obviously responsible for the formation of the observed phosphane low coordinated PtCl 2L2 species. The same responsible for the formation of the observed phosphane low coordinated PtCl2 L2 species. The same reasoncan canalso alsoexplain explainthe thetrans transgeometry geometry obtained obtained for for these these species reason species instead insteadof ofthe thecis cisone one[18]. [18]. Cl

= ortho-substituted phosphane

Pt Cl

1 1JP–Pt

= 2590 Hz free phosphane

a) 1 1JP–Pt

= 2750 Hz free phosphane

b) 45

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31 31 1 H} Figure spectra of Kof + 3 equiv. of (a) tris(o-Me)TPPTS or (b) tris(o-OMe)TPPTS 2 PtCl 4 (3 mM) Figure3.3. P{ P{1H}NMR NMR spectra K2PtCl 4 (3 mM) + 3 equiv. of (a) tris(o-Me)TPPTS or (b) tris(o◦ atOMe)TPPTS 25 C in D2 O. at 25 °C in D2O.

1H} NMR spectrum of cis-PtCl2(TPPTS)2, [Pt] = 10 mM, 25 °C 3131 1 H} Figure inin D2D O.2 O. Figure 4. 4. P{P{ NMR spectrum of cis-PtCl2 (TPPTS)2 , [Pt] = 10 mM, 25 ◦ C

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Trisulfonated Biphenylphosphane Trisulfonated BiphenylphosphaneLigands Ligands Again, [PtL complex was obtained by by adding three equivalents of the ligand Again, [PtL 3Cl]Cl complex was obtained adding three equivalents of monobiphenyl the monobiphenyl 3 Cl]Cl ligand P(Biph)Ph 2 TS to a K 2 PtCl 4 aqueous solution. However, when P(Biph) 2 PhTS and P(Biph) 3were TS P(Biph)Ph TS to a K PtCl aqueous solution. However, when P(Biph) PhTS and P(Biph) TS 2 2 4 2 3 31 1 31P{1H} NMR spectra. Addition of DMSO were used, the complexes appeared as broad signals in the used, the complexes appeared as broad signals in the P{ H} NMR spectra. Addition of DMSO to the to the previous solutions achieves finer signals 5). previous aqueousaqueous solutions achieves finer signals (Figure(Figure 5).

L = P(Biph)Ph2TS

a) (ppm)

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phosphane oxide

a)

phosphane oxide

L = P(Biph)2PhTS

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free L

c) (ppm)

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c) (ppm)

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31 P{1 H} NMR spectra of K PtCl solution (10 mM) + 3 equiv. of ligand (L) at 25 ◦ C (a) in D O Figure 5. 5. 31P{1H} NMR spectra of K22PtCl44 solution (10 mM) + 3 equiv. of ligand (L) at 25 °C (a) in D2O2 Figure (b)(b) in in D2D O/DMSO-d (50/50vol.) vol.)(c)(c)ininDMSO-d DMSO-d . 66 mixture 2O/DMSO-d mixture (50/50 6. 6

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In pure pureDMSO, DMSO,cis-PtCl cis-PtCl2LL2 is is formed formed quantitatively quantitatively ((11JP–Pt JP–Pt == 3696 3696 Hz Hz when whenLL==P(Biph) P(Biph)2PhTS PhTS In 2 2 2 1JP–Pt = 3702 Hz when L = P(Biph)3TS). The lowest DMSO polarity compared to water is probably and 1 and JP–Pt = 3702 Hz when L = P(Biph)3 TS). The lowest DMSO polarity compared to water is probably responsiblefor forthe theformation formationofofthese thesenon-ionic non-ioniccomplexes. complexes.When When the water quantity medium responsible the water quantity of of thethe medium is is increased, the polarity increases as well probably leading to the formation of [PtL 3Cl]Cl. With these increased, the polarity increases as well probably leading to the formation of [PtL3 Cl]Cl. With these twoligands, ligands,fast fastexchange exchangebetween between [PtLCl]Cl 3Cl]Cl complex and water molecules would be responsible two [PtL complex and water molecules would be responsible for 3 for the signals broadening. the signals broadening. 2.1.2. RAME-β-CD RAME-β-CD Effects Effects on on the the Coordination Coordination Behaviour Behaviour of of the the Ligands Ligands 2.1.2. As aa reminder reminder of of our our previous previous work, work, Table Table11brings bringstogether togetherthe theassociation associationconstants constants between between As the different hydrosoluble ligands studied and the CDs [15]. the different hydrosoluble ligands studied and the CDs [15]. TPPTS Ligand Ligand TPPTS When1equiv. 1equiv.of ofRAME-β-CD RAME-β-CDtoward towardplatinum platinumwas wasadded addedto toaasolution solutionof ofthe the[Pt(TPPTS) [Pt(TPPTS)33Cl]Cl Cl]Cl When complex, aa downfield downfield chemical chemical shift shift of of the the TPPTS TPPTS oxide oxide signal signal was was observed observed and and attributed attributed to to the the complex, formationof ofan an inclusion inclusion complex complexwith withRAME-β-CD RAME-β-CD [19]. [19]. Moreover, Moreover, aa typical typical signal signal of of CD-included CD-included formation TPPTSappeared appearedat at− −8.8 TPPTS 8.8 ppm as well as a cis-PtCl22(TPPTS) (TPPTS)22 signal signalat at15.5 15.5ppm ppm (Figure (Figure 6). 6).

phosphane oxide

a)

CD included phosphane

b)

PtCl2L2

c)

d) 40

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(ppm)

31P{11H} Figure H} NMR NMR spectra of (a) [Pt(TPPTS) Figure6.6. 31 [Pt(TPPTS)33Cl]Cl (10 mM); (b) +3 +3 equiv. equiv. of of RAME-β-CD RAME-β-CD toward toward Pt C in D22O. O. Pt(c) (c)+6 +6 equiv. equiv. of of RAME-β-CD RAME-β-CD and and (d) (d) +12 +12 equiv. equiv. of of RAME-β-CD RAME-β-CD at 25 ◦°C

By adding CDCD (3 to thesethese signals are intensified. Thus, RAMEBy adding increasing increasingamounts amountsofof (3 12 toequiv.), 12 equiv.), signals are intensified. Thus, β-CD is able is toable modify the equilibrium between thesethese two organometallic species. In particular, the RAME-β-CD to modify the equilibrium between two organometallic species. In particular, formation of phosphane low-coordinated organometallic species is favoured by the formation of an the formation of phosphane low-coordinated organometallic species is favoured by the formation of inclusion complex between RAME-β-CD and (equilibrium (1) (1) is is an inclusion complex between RAME-β-CD andTPPTS TPPTSasasdepicted depictedininScheme Scheme 22 (equilibrium displacedby byequilibrium equilibrium (2)). Note behaviour is similar is observed by high displaced (2)). Note thatthat suchsuch behaviour is similar to whattoiswhat observed by high pressure pressure NMR when RAME-β-CD added, under hydroformylation conditions (50 bars CO/H2 ◦and NMR when RAME-β-CD is added,isunder hydroformylation conditions (50 bars CO/H 2 and 80 C),

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8080 °C), 3 rhodium complex. In that case, HRh(CO)2(TPPTS)2 species °C), on on the the HRh(CO)(TPPTS) HRh(CO)(TPPTS) 3 rhodium complex. In that case, HRh(CO)2(TPPTS)2 species on the HRh(CO)(TPPTS) rhodium complex. In that case, HRh(CO)2 (TPPTS)2 species combined with combined with TPPTS included in the 3 combined with TPPTS included in theCD CDcavity cavitywere werehighlighted highlighted[10]. [10]. TPPTS included in the CD cavity were highlighted [10].

Scheme Scheme2.2.Equilibria Equilibriabetween betweenthe thedifferent differentplatinum platinumspecies specieswith withTPPTS TPPTSasasligand ligandininthe thepresence presenceofof 3131 1H} RAME-β-CD (species observed on the P{ NMR spectrum are presented on a grey background). 1 31 1 RAME-β-CD (species observed on the P{ P{ H} H}NMR NMRspectrum spectrumare arepresented presentedon onaagrey greybackground). background).

The 3Cl]Cl into cis-PtCl2(TPPTS)2 as a function of the RAME-β-CD Theconversion conversionofof of[Pt(TPPTS) [Pt(TPPTS) 3Cl]Cl into cis-PtCl2(TPPTS)2 as a function of the RAME-β-CD The conversion [Pt(TPPTS) (TPPTS) 3 Cl]Cl into cis-PtCl231 2 as a function of the RAME-β-CD 1H} NMR quantity (Figure 7) can be measured by P{P{ spectra (see ESI). As expected, 31 1 quantity (Figure (Figure 7) 7) can can be be measured measured by byintegration integrationof ofthe the 31 quantity integration of the P{1H} H} NMR NMR spectra spectra (see (see ESI). ESI). As As expected, expected, the conversion increases with the quantity ofofRAME-β-CD ininsolution. The temperature also has the conversion increases with the quantity RAME-β-CD solution. The temperature also hasan an the conversion increases with the quantity of RAME-β-CD in solution. The temperature also has influence on these equilibria. Indeed, the conversion increases with the temperature, therefore, influence on these equilibria. Indeed, the conversion increases with the temperature, therefore, an influence on these equilibria. Indeed, the conversion increases with the temperature, therefore, implying 3Cl]Cl is more affected compared to implyingthat thatthe thenatural naturaldissociation dissociationofof ofTPPTS TPPTSfrom from[Pt(TPPTS) [Pt(TPPTS) 3Cl]Cl is more affected compared to implying that the natural dissociation TPPTS from [Pt(TPPTS) 3 Cl]Cl is more affected compared to the inclusion complex stability. Moreover, the NMR spectrum carried out the inclusion complex stability. Moreover, the NMR spectrum carried outatat atroom roomtemperature temperatureafter after the inclusion complex stability. Moreover, the NMR spectrum carried out room temperature after heating gave back the signals with the same initial intensity reflecting the process reversibility and heating gave back the signals with the same initial intensity reflecting the process reversibility and heating gave back the signals with the same initial intensity reflecting the process reversibility and assuming a thermodynamic control of the system. assuming aa thermodynamic thermodynamic control control of of the the system. system. assuming Pt conversion (%) Pt conversion (%)

T(°C) T(°C) CD/Pt CD/Pt

40 40

0

30 30

T (°C) T (°C)

3

20 20 10 10

85 85 60 60

0

9

40 40

6 25 25 0

3

12 12 9

0

Rame-β-CD Rame-β-CD Pt Pt

6 9

0 3 6

9 12 12

25 25

40 40

60 60

85 85

0

0

0

0

0 9.2 9.2 10.4 10.4 13.9 13.9 14.7 14.7

0 9.5 9.5 14.7 14.7 17.9 17.9 18.8 18.8

0 9.9 9.9 18 18 20.0 20.0 23.1 23.1

0 17.3 17.3 22.0 22.0 24.8 24.8 28.4 28.4

6

3

0

Figure 7. [Pt(TPPTS)3 Cl]Cl conversion (%) into cis-PtCl2 (TPPTS)2 as a function of RAME-β-CD quantity Figure 7. [Pt(TPPTS)3Cl]Cl conversion (%) into cis-PtCl2(TPPTS)2 as a function of RAME-β-CD Figure 7. [Pt(TPPTS) conversion (%) into cis-PtCl2(TPPTS)2 as a function of RAME-β-CD and temperature, [Pt] 3=Cl]Cl 10 mM, D2 O. quantity and temperature, [Pt] = 10 mM, D2O. quantity and temperature, [Pt] = 10 mM, D2O.

para-Substituted TPPTS Derivatives para-Substituted para-SubstitutedTPPTS TPPTSDerivatives Derivatives The behaviour of tris(p-OMe)TPPTS and tris(p-Me)TPPTS towards RAME-β-CD is different. The ofoftris(p-OMe)TPPTS and towards RAME-β-CD isisdifferent. Thebehaviour behaviour tris(p-OMe)TPPTS andtris(p-Me)TPPTS tris(p-Me)TPPTS different. Indeed, unlike tris(p-OMe)TPPTS, tris(p-Me)TPPTS forms an towards inclusionRAME-β-CD complex with this CD Indeed, unlike tris(p-OMe)TPPTS, tris(p-Me)TPPTS forms an inclusion complex with this CD (K Indeed, unlike tris(p-OMe)TPPTS, tris(p-Me)TPPTS forms an inclusion complex with this CD (K=to=960 960 − 1 (K = 960 M ) [15]. The highest association constant of this inclusion complex compared the −1) [15]. The highest association constant of this inclusion complex compared to the complex RAMEMM −1) [15]. The highest association constant − of this inclusion complex compared to the complex RAME1 complex RAME-β-CD/TPPTS (K = 840 M ) is due to the deep inclusion of the tris(p-Me)TPPTS via −1) is due β-CD/TPPTS (K = =840 MM deep −1) is dueto β-CD/TPPTS 840into tothe the[20]. deepinclusion inclusionofofthe thetris(p-Me)TPPTS tris(p-Me)TPPTSvia viaone oneofofitsitsaryl aryl one of its aryl (K groups the CD cavity groups into the CD cavity [20]. groups into the CD cavity [20]. Given that the tris(p-OMe)TPPTS does not interact with RAME-β-CD, it is not surprising to see Given tris(p-OMe)TPPTS does not with Giventhat thatthe the notinteract interact withRAME-β-CD, RAME-β-CD,ititisisnot notsurprising surprisingtotosee see no modifications ontris(p-OMe)TPPTS the3131 P{1 1 H} NMR does spectrum of the [Pt(tris(p-OMe)TPPTS) 3 Cl]Cl organometallic no modifications on the P{ H} NMR spectrum of the [Pt(tris(p-OMe)TPPTS) 3Cl]Cl organometallic 31 1 no modifications on the P{ H} NMR spectrum of the [Pt(tris(p-OMe)TPPTS) 3Cl]Cl organometallic complex when the RAME-β-CD was added (see ESI). Surprisingly, the same behaviour was observed complex when was added the same was observed complex whenthe theRAME-β-CD RAME-β-CD was added(see (seeESI). ESI).Surprisingly, Surprisingly, the samebehaviour behaviour observed with the tris(p-Me)TPPTS ligand. Indeed, although the association constant between was RAME-β-CD with the tris(p-Me)TPPTS ligand. Indeed, although the association constant between RAME-β-CD with the tris(p-Me)TPPTS ligand. Indeed, although the association constant between RAME-β-CD and andtris(p-Me)TPPTS tris(p-Me)TPPTSisishigher higherthan thanthe theone onebetween betweenRAME-β-CD RAME-β-CDand andTPPTS, TPPTS,no noconversion conversionofof

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and tris(p-Me)TPPTS is higher than the one between RAME-β-CD and TPPTS, no conversion of [Pt(tris(p-Me)TPPTS) to 2PtCl was highlighted after the addition of [Pt(tris(p-Me)TPPTS) 3Cl]Cl to PtCl (tris(p-Me)TPPTS) 2 was2 highlighted after the addition of RAME3 Cl]Cl 2 (tris(p-Me)TPPTS) RAME-β-CD, even temperature at high temperature can be by explained by σ-donating the higher β-CD, even at high (see ESI) (see [21]. ESI) This [21]. resultThis can result be explained the higher σ-donating strength of tris(p-Me)TPPTS ligand, to compared to TPPTS. Consequently, the equilibrium (1) strength of tris(p-Me)TPPTS ligand, compared TPPTS. Consequently, the equilibrium (1) is shifted is shifted towards the formation of the high coordinated platinum species [Pt(tris(p-Me)TPPTS) Cl]Cl towards the formation of the high coordinated platinum species [Pt(tris(p-Me)TPPTS)3Cl]Cl even in 3 even in the presence of RAME-β-CD 3). the presence of RAME-β-CD (Scheme(Scheme 3).

Scheme 3. Equilibria Equilibriabetween betweenthe thedifferent differentplatinum platinum species with tris(p-Me)TPPTS as ligand in species with tris(p-Me)TPPTS as ligand in the 311 P{1 H} NMR spectrum are presented on 31P{ the presence of RAME-β-CD (species observed H} NMR spectrum are presented on a presence of RAME-β-CD (species observed on on thethe agrey greybackground). background).

Ortho-Substituted TPPTS TPPTS Derivatives Derivatives Ortho-Substituted do not interact interact with with RAME-β-CD RAME-β-CD [15,20], addition of CD did Since the ortho-substituted ligands do 31P{ the 31 not modify the P{11H} H}NMR NMR spectra. spectra. Trisulfonated Trisulfonated Biphenylphosphane Biphenylphosphane Ligands Ligands Phosphanes Phosphanes possessing possessing one, one, two two or or three three sulfonated sulfonated biphenyl biphenyl groups groups strongly strongly interact interact with with the the β-CD. Indeed, complexation studies between these ligands and native β-CD showed a deep inclusion β-CD. Indeed, complexation studies between these ligands and native β-CD showed a deep inclusion of the CD cavity. In all stoichiometries werewere determined to be to equal to 1:1 of their theirbiphenyl biphenylmoiety moietyinin the CD cavity. In cases, all cases, stoichiometries determined be equal and association constants were particularly high (Table 1 and Supplementary Materials). Consequently, to 1:1 and association constants were particularly high (Table 1 and Supplementary Materials). the influence ofthe such association towards the platinum complexes wascomplexes investigated. Consequently, influence of such association towardsorganometallic the platinum organometallic was In the case of P(Biph)Ph2 TS, modifications on the 31 P{1 H} NMR spectra are observed with investigated. RAME-β-CD addition. Complexation of the phosphane oxide byspectra the CDare is observed in fact detected by its In the case of P(Biph)Ph 2TS, modifications on the 31P{1H} NMR with RAMEchemical shift modification. Moreover, a broadening [PtL observed 3 Cl]Cl β-CD addition. Complexation of the phosphane oxideofby the CD issignals in factisdetected byconcurrently its chemical with the lack of peak corresponding to free or CD-complexed phosphane (in the region going from shift modification. Moreover, a broadening of [PtL3Cl]Cl signals is observed concurrently with the 0lack to − 10 ppm) (Figure 8). The explanation for that is the interaction between RAME-β-CD of peak corresponding to free or CD-complexed phosphane (in the region going from 0 toand −10 [Pt(P(Biph)Ph inducing of theinteraction ligand frombetween the metal RAME-β-CD centre. This theory 2 TS) 3 Cl]Cl ppm) (Figure 8). Thewithout explanation fordissociation that is the and was confirmed by the 2D T-ROESY experiment of a 1:1 β-CD:[Pt(P(Biph)Ph TS) Cl]Cl [22] mixture [Pt(P(Biph)Ph2TS)3Cl]Cl without inducing dissociation of the ligand from2 the 3metal centre. This which intenseby cross-peaks betweenexperiment the phosphane protons and the internal CD theory exhibited was confirmed the 2D T-ROESY of a aromatic 1:1 β-CD:[Pt(P(Biph)Ph 2TS) 3Cl]Cl [22] protons H5 ). In that case,cross-peaks an organometallic formation where the CD plays mixture (H which intense betweencomplex the phosphane aromatic protons and the 3 andexhibited role of coordination is highlighted (Scheme 4). Thus, contrary TPPTS, three internal CD protonssecond (H3 andsphere H5). Inligand that case, an organometallic complex formationtowhere the CD equivalents of RAME-β-CD with respect to Pt are not able to transform the [PtL4). into plays the role of coordination second sphere ligand is highlighted (Scheme Thus,complex contrary to 3 Cl]Cl PtCl L complex when P(Biph)Ph TS is used. Nevertheless, further increase in the CD quantity TPPTS, three equivalents of RAME-β-CD with respect to Pt are not able to transform the [PtL 3 Cl]Cl 2 2 2 (12 equivalents of 2RAME-β-CD relative to Pt) and (85 ◦ C) lead to a dissociation of CD the complex into PtCl L2 complex when P(Biph)Ph 2TS temperature is used. Nevertheless, further increase in the ligand from metal centre confirmed both by theto CD-included phosphane observed at −3 ppm quantity (12the equivalents of RAME-β-CD relative Pt) and temperature (85signal °C) lead to a dissociation and the formation of low-coordinated PtCl L species (Figure 8c). of the ligand from the metal centre confirmed 2 2 both by the CD-included phosphane signal observed theand other whenofP(Biph) P(Biph) used,8c). addition of large amounts at −3On ppm thehand, formation low-coordinated 2L2 species (Figure 2 PhTS andPtCl 3 TS were of CDOn to the the other complexes by2PhTS adding three equivalents ofused, the previous a K2 PtClof4 hand,synthetized when P(Biph) and P(Biph) 3TS were additionligands of largetoamounts aqueous solution did not lead to a signal improvement (obtained spectra were comparable CD to the complexes synthetized by adding three equivalents of the previous ligands to ato K2those PtCl4 presented in Figure 5(a)), in these cases,improvement it is difficult to(obtained conclude.spectra were comparable to those aqueous solution did not so lead to a signal

presented in Figure 5(a)), so in these cases, it is difficult to conclude.

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Figure 8. 31 P{311 H}1 NMR spectra of (a) [Pt(P(Biph)Ph2 TS)3 Cl]Cl 10 mM; (b) +3 equiv. of RAME-β-CD Figure 8. P{ H} NMR spectra of (a) [Pt(P(Biph)Ph2TS)3Cl]Cl 10 mM; (b) +3 equiv. of RAME-β-CD toward Pt at 25 ◦ C (c) +12 equiv. of RAME-β-CD toward Pt at 85 ◦ C (d) 2D T-ROESY spectrum of toward Pt at 25 °C (c) +12 equiv. of RAME-β-CD toward Pt at 85 °C (d) 2D T-ROESY spectrum of a ◦ C in D O. a solution containing [Pt(P(Biph)Ph mM) at°C 25in 2 TS) 3 Cl]Cl 2TS) 3Cl]Cl (10(10 mM) at 25 D2O. 2 solution containingβ-CD β-CD(10 (10 mM) mM) and and [Pt(P(Biph)Ph

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(1) (1) ++

(3) (3)

(2) (2)

P(Biph)Ph P(Biph)Ph2TS 2TS

Scheme 4. Equilibria between the different platinum species with P(Biph)Ph2TS as ligand in the

Scheme 4. Equilibria between the different platinum species with P(Biph)Ph 2 TS as ligand in the presence of 3 equiv. of RAME-β-CD toward Pt (species observed on the 3131 P{1H} NMR spectrum are presence of 3 equiv. of RAME-β-CD toward Pt (species observed on the P{1 H} NMR spectrum are oror presented on a grey background). presented on a grey background).

Scheme 4. Equilibria between the different platinum species with P(Biph)Ph2TS as ligand in the

Scheme 4. Equilibriaofbetween the different platinum species with P(Biph)Ph 2TS as ligand in the A short overview platinum study is presented in Table 2. To sum up, 31P{ 1H}low-coordinated Scheme 4. Equilibria the different platinum species with P(Biph)Ph ligand in the presence ofbetween 3this equiv. of RAME-β-CD toward Pt (species observed on2TS theas NMR spectrum are Scheme 4.4. Equilibria between the platinum species with 2TS in the Scheme Equilibria between the different different platinum species P(Biph)Ph 2TS as as ligand ligand 31P(Biph)Ph 1H} NMR presence of 3 equiv. of RAME-β-CD toward Pt (species observed on with the 31 P{ spectrum arein the 1H} A short overview of this platinum study is presented in Table 2. To sum up, low-coordinated catalytic species PtCl 2 L 2 are formed when ortho-substituted TPPTS derivatives arespectrum used when 31 1 presence of 3 equiv. of RAME-β-CD toward Pt (species observed on the P{ NMR spectrum are or 31 1H}NMR presented on aofof grey background). presence ofof33equiv. RAME-β-CD toward Pt (species observed on the P{ H} are presence equiv. RAME-β-CD toward Pt (species observed on the P{ NMR spectrum are presented on a grey background). presented on a grey background). TPPTS-based complexes are combined with ortho-substituted RAME-β-CD (trans TPPTS and cis geometry respectively). catalytic species PtCl are formed when derivatives are used In or the when presented on aa2grey background). 2L presented on grey background). A short overview of this platinum study is presented in Table 2. To sum up, low-coordinated first case, these species are obviously formed due to the larger cone angles of these ortho-substituted TPPTS-based complexes are combined with RAME-β-CD (trans and cis geometry respectively). In the A short overview of this platinum study is presented in Table 2. To sum up, low-coordinated A short overview of this platinum study iswhen presented inofTable 2. ToTPPTS up, low-coordinated AAcatalytic short overview of this study presented in Table 2.2.sum To up, low-coordinated species PtCl 2L2platinum are formed ortho-substituted derivatives are presence used or when short overview of this platinum study ispower presented incone Table Tosum sum up, low-coordinated In the second the relative σ-donating the TPPTS ligand, through the firstligands. case, these species obviously formed dueisto the larger angles ofare these ortho-substituted catalytic species PtCl 2are Lcase, 2 are formed when ortho-substituted TPPTS derivatives used or when catalytic species PtClsodium 2PtCl L 2complexes are ortho-substituted TPPTS derivatives are used or when species 2L 2 2formed are when ortho-substituted TPPTS derivatives are or when TPPTS-based arewhen combined with RAME-β-CD (trans and cisweak geometry respectively). catalytic species PtCl 2L are formed formed when ortho-substituted derivatives are used used or whenIn the of thecatalytic attractive meta sulfonato groups, makes the ligand-metal bond and hence RAMETPPTS-based complexes are combined with RAME-β-CD (trans and cis geometry respectively). In the ligands. In the second case, the relative σ-donating power ofand theTPPTS TPPTS ligand, through the presence TPPTS-based complexes are combined with RAME-β-CD (trans cis geometry respectively). In the TPPTS-based complexes are combined with RAME-β-CD (trans and cis geometry respectively). In the first case, these species are obviously formed due to the larger cone angles of these ortho-substituted TPPTS-based complexes are combined with RAME-β-CD (trans and cis geometry respectively). In the β-CD is able to shift the equilibria between the different organometallic the formation first case, these species are obviously formed due to the larger cone anglesspecies of thesetowards ortho-substituted of the meta sodium sulfonato groups, makes the bond weak and hence firstattractive case, these species aresecond obviously formed due due to the larger coneligand-metal angles of these ortho-substituted first case, these species are obviously formed to the larger cone angles of these ortho-substituted ligands. In the case, the relative σ-donating power of the TPPTS ligand, through the presence first case, these species are obviously formed due to the larger cone angles of these ortho-substituted of low-coordinated species by the formation of inclusion complex withthrough the ligand. However, ligands. In the second case, the relative σ-donating power of the TPPTS ligand, thespecies presence RAME-β-CD is able to shift the equilibria between the different organometallic towards ligands. In of thethe case,meta the relative σ-donating power of the ligand, through the presence ligands. the second case, the relative σ-donating power of the TPPTS ligand, the attractive sodium sulfonato groups, makes the ligand-metal bond weak and hence RAMEInsecond the second case, thebetween relative σ-donating ofTPPTS the TPPTS ligand, through thepresence presence although theIn association constant tris(p-Me)TPPTS and RAME-β-CD isthrough higher the one of theligands. attractive meta sodium sulfonato groups, makes thepower ligand-metal bond weak and hencethan RAMEof the attractive meta sodium sulfonato groups, thedifferent ligand-metal bondbond weak and hence RAMEthe formation of low-coordinated species bymakes themakes formation of inclusion complex with the ligand. of the attractive meta groups, the ligand-metal weak and hence RAMEβ-CD is able tosodium shift thesulfonato equilibria between the organometallic species towards the formation of the attractive meta sodium sulfonato groups, makes the ligand-metal bond weak and hence RAMEbetween TPPTS andthe RAME-β-CD, low-coordinated complexes are not observed. β-CD is able to shift equilibria between the differentplatinum organometallic species towards the formation

β-CDβ-CD isalthough able to shift the equilibria between different organometallic species towards the formation is to the between the different organometallic species towards the of low-coordinated species bythe the formation of inclusion complex with the ligand. However, However, the association constant between tris(p-Me)TPPTS and RAME-β-CD isformation higher than β-CD isable able toshift shift theequilibria equilibria between the towards the formation of low-coordinated species by the formation of different inclusionorganometallic complex withspecies the ligand. However, of low-coordinated species by the formation of inclusion complex with ligand. However, Table 2. Organometallic species formed by adding 3 equiv. of ligand to a K 2the PtCl 4the aqueous solution of low-coordinated species by the formation of inclusion complex with the ligand. However, although the association constant between tris(p-Me)TPPTS and RAME-β-CD is higher than the one of low-coordinated species by the formation of inclusion complex with ligand. However, the one between TPPTS and RAME-β-CD, low-coordinated complexes not although the association constant between tris(p-Me)TPPTS andplatinum RAME-β-CD is higherare than theobserved. one although the association constant between tris(p-Me)TPPTS and RAME-β-CD is higher thanobserved. the (10 mM) and RAME-β-CD addition (1low-coordinated totris(p-Me)TPPTS 12 equiv. toward platinum). although the after association constant between and isis higher than the between TPPTS and RAME-β-CD, platinum complexes are not although association constant between tris(p-Me)TPPTS andRAME-β-CD RAME-β-CD higher thanone theone one between TPPTSthe and RAME-β-CD, low-coordinated platinum complexes are not observed. between and and RAME-β-CD, low-coordinated platinum complexes area not observed. between TPPTS RAME-β-CD, low-coordinated platinum complexes are not observed. between TPPTS and RAME-β-CD, low-coordinated platinum complexes are not observed. Organometallic species formed by adding 3 equiv. of ligand to K PtCl aqueous solution Table 2. TPPTS 2to a K42PtCl4 aqueous solution Table 2. Organometallic formed by adding 3New equiv. of ligand Platinumspecies Complex Species Obtained Table 2. Organometallic species formed by adding 3 equiv. of ligand to a K2PtCl4 aqueous solution Ligand (10 mM) and after RAME-β-CD addition (1addition toby 12adding equiv. toward platinum). TableTable 2. Organometallic formed by adding 3(1equiv. of ligand to a K 2PtCl aqueous solution Obtained without CD after RAME-β-CD Addition (10 mM) and species after RAME-β-CD to3312 equiv. toward platinum). 2. species formed equiv. ofof ligand to aaKK24PtCl 4 4aqueous solution Table 2.Organometallic Organometallic species formed by adding equiv. ligand to 2PtCl aqueous solution (10 mM) and after RAME-β-CD addition (1 to 12 equiv. toward platinum). (10 mM) and RAME-β-CD addition (1=to (1 12 equiv. toward platinum). (10 and addition toward platinum). (10mM) mM)after andafter afterRAME-β-CD RAME-β-CD addition (1to to12 12equiv. equiv. toward platinum). [PtL 3Cl]Cl Platinum Complex New 2Species Obtained L2 = cis-PtCl New New Species Obtained Platinum Complex Species Obtained Ligand Ligand Platinum Complex New Species Obtained Ligand Obtained without CD after RAME-β-CD Addition Platinum Complex New Species Obtained Platinum New Species Obtained Obtained withoutComplex CD RAME-β-CD Addition Ligand after after RAME-β-CD Addition Ligand Ligand Obtained TPPTS without CD3Cl]Cl after after RAME-β-CD Addition Obtained without CD Addition Obtained without CD= afterRAME-β-CD RAME-β-CD Addition [PtL cis-PtCl2L2 = [PtL [PtL3Cl]Cl = cis-PtCl2L2 = [PtL33[PtL Cl]Cl = [PtL3Cl]Cl 3Cl]Cl== 2L2 = 2L2 = cis-PtCl cis-PtCl cis-PtCl 2L2 = TPPTS TPPTS TPPTS TPPTS tris(p-Me)TPPTS [PtL3Cl]Cl TPPTS TPPTS cis-PtCl2 L2- = tris(p-OMe)TPPTS [PtL3Cl]Cl tris(p-Me)TPPTS 2L2[PtL = 3Cl]Cl trans-PtCl tris(p-Me)TPPTS [PtL3Cl]Cl tris(p-Me)TPPTS [PtL Cl]Cl [PtL3Cl]Cl tris(p-Me)TPPTS [PtL33[PtL Cl]Cl tris(p-OMe)TPPTS tris(p-Me)TPPTS 3Cl]Cl tris(p-Me)TPPTS [PtL 3Cl]Cl tris(p-OMe)TPPTS [PtL3Cl]Cl tris(o-Me)TPPTS tris(p-OMe)TPPTS tris(p-OMe)TPPTS Cl]Cl tris(p-OMe)TPPTS tris(p-OMe)TPPTS [PtL33[PtL [PtL3Cl]Cl 3Cl]Cl 2L 2 = trans-PtCl trans-PtCl2L2 = 2L2 2 = trans-PtCl trans-PtCl = trans-PtCl 2L 2 2== 2 trans-PtCl 2 L tris(o-Me)TPPTS tris(o-Me)TPPTS tris(o-OMe)TPPTS trans-PtCl2L2 tris(o-Me)TPPTS tris(o-Me)TPPTS tris(o-Me)TPPTS tris(o-Me)TPPTS tris(o-OMe)TPPTS trans-PtCl2L2 tris(o-OMe)TPPTS trans-PtCl2L2 tris(o-OMe)TPPTS trans-PtCl 2L L22 2L tris(o-OMe)TPPTS trans-PtCl tris(o-OMe)TPPTS trans-PtCl tris(o-OMe)TPPTS trans-PtCl 2 P(Biph)Ph2TS [PtL3Cl]Cl 2L2 2 P(Biph)Ph2TS [PtL3Cl]Cl P(Biph)Ph2TS [PtL3Cl]Cl P(Biph)Ph 2TS 2TS [PtL 3[PtL Cl]Cl P(Biph)Ph 3 Cl]Cl P(Biph)Ph TS [PtL Cl]Cl P(Biph)Ph 2 TS [PtL 3 Cl]Cl 2 3

P(Biph)2PhTS P(Biph)3TS

n.d (broad signals) * n.d (broad signals) *

-

----

-

- --

-

---

-

-

or n.d (broad signals) or or n.d (broad signals) or or or or

P(Biph)2PhTS n.d (broad signals) * n.d (broad signals) P(Biph) 2PhTS n.d (broad signals) * n.d (broad signals) * Probably [PtL3Cl]Cl when compared with obtained with P(Biph)Ph 2TS. P(Biph) 2PhTS n.d signals) * signals) n.d (broad signals) P(Biph) 3TS(broad n.d (broad * n.d (broad signals) P(Biph) 2PhTS n.d (broad signals) ** spectrum n.d (broad signals) P(Biph) PhTS (broad signals) * n.d (broad signals) P(Biph) 2PhTS n.d n.d (broad signals) n.d (broad signals) 2 P(Biph)3TS n.d (broad signals) * n.d (broad signals) P(Biph) 3TS 3TS n.d (broad signals) * n.d (broad signals) P(Biph) n.d (broad signals) * n.d (broad signals) * Probably [PtL 3 Cl]Cl when compared with spectrum obtained with P(Biph)Ph 2TS. P(Biph)3TS n.d (broad n.d (broad signals) * n.d (broad (broadsignals) signals) P(Biph) signals) * with n.d 3 TS * Probably [PtL3Cl]Cl when compared spectrumpower obtained with P(Biph)Ph 2TS. This behaviour comes from the highest σ-donating of this ligand compared to TPPTS * Probably [PtL 3[PtL Cl]Cl when compared with spectrum obtained with P(Biph)Ph 2TS. 2TS. **Probably 3 Cl]Cl when compared with spectrum obtained with P(Biph)Ph Probably 3Cl]Cl when compared with spectrum obtained with P(Biph)Ph2TS. * Probably [PtL[PtL 3 Cl]Cl when compared with spectrum obtained with P(Biph)Ph2 TS.

through the presence of the donating para which makes theligand ligand-metal This behaviour comes from themethyl highest groups σ-donating power of this comparedbond to TPPTS This behaviour comes from the highest σ-donating power of this ligand compared to TPPTS ThisThis behaviour comes fromfrom the highest σ-donating power of this ligand compared TPPTS stronger. Furthermore, given that tris(p-OMe)TPPTS does not interact with RAME-β-CD, its bond behaviour comes the highest σ-donating power of this compared to through the presence of the para methyl groups which makes thetoligand-metal This behaviour comes from thedonating highest σ-donating power of thisligand ligand compared toTPPTS TPPTS

through the presence of the donating para methyl groups which makes the ligand-metal bond through the presence of the para methyl groups which makes ligand-metal bond This behaviour comes from the highest σ-donating power of this ligand compared tobond TPPTSits through the of the donating para methyl groups which makes the ligand-metal stronger. Furthermore, given that tris(p-OMe)TPPTS does notthe interact with RAME-β-CD, through the presence presence of donating the para methyl groups ligand-metal stronger. Furthermore, given thatdonating tris(p-OMe)TPPTS does not which interactmakes with the RAME-β-CD, itsbond stronger. Furthermore, given that tris(p-OMe)TPPTS does not interact with RAME-β-CD, its through stronger. the presence of the donating para methyl groups which the ligand-metal bond stronger. Furthermore, given does not with its stronger. Furthermore, given that that tris(p-OMe)TPPTS tris(p-OMe)TPPTS doesmakes not interact interact with RAME-β-CD, RAME-β-CD, its

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Furthermore, given that tris(p-OMe)TPPTS does not interact with RAME-β-CD, its coordination behaviour towards platinum(II) is not affected by the CD addition. Finally, formation of organometallic species where the RAME-β-CD plays the role of coordination second sphere ligand is observed when P(Biph)Ph2 TS, which possesses a CD-recognised moiety, is used in combination with one equivalent of RAME-β-CD towards the ligand. It is important to emphasize that further increase in the CD quantity yields to the formation of low-coordinated species. The formation of organometallic species possessing more than one CD in their coordination second sphere would probably yield to a steric decompression trough the decoordination of the CD included phosphane. 2.2. Palladium Complexes The RAME-β-CD influence on organometallic species was extended to palladium (0) complexes. The palladium extraction from a toluene solution of Pd(TPP)4 to an aqueous phase by the hydrosoluble ligand yields to isolation of PdLx complexes (see “materials and methods” part). In the case of TPPTS, this study has already been published by our group [19]. It was concluded that the addition of RAME-β-CD only yields to a chemical exchange rate decrease between free TPPTS and the Pd(TPPTS)3 complex caused by the formation of the inclusion complex RAME-β-CD/TPPTS. Furthermore, no new palladium species were observed, even at high temperature (60 ◦ C). 2.2.1. Para-Substituted TPPTS Derivatives [Pd(0)/tris(p-Me)TPPTS] Complex 31 P{1 H}

NMR spectra of Pd(tris(p-Me)TPPTS)3 complexes in addition to different RAME-β-CD concentrations and at different temperatures are given in Figure 9. Without CD, two different resonances are observed. Besides the minor phosphane oxide signal at 34 ppm, a broad signal was detected at 19.5 ppm which corresponds to the average signal of the Pd(tris(p-Me)TPPTS)3 complex in fast equilibrium with a small amount of free residual tris(p-Me)TPPTS ligand [19,23]. Higher temperatures have no effects on this equilibrium. Adding three equivalents of RAME-β-CD yields to an exchange rate decrease between the Pd(tris(p-Me)TPPTS)3 species, which signal becomes sharp at 21.8 ppm, and the small excess of free ligand by its encapsulation in the CD cavity (−11.2 ppm). Higher CD concentrations combined with higher temperatures do not lead to the formation of new palladium species. Hence, like what was observed with the platinum(II) complexes, addition of RAME-β-CD does not change the nature of the organometallic complex, albeit association constant between the CD and the ligand is greater than that of the RAME-β-CD/TPPTS inclusion complex. [Pd(0)/tris(p-OMe)TPPTS] Complex Addition of large amount of RAME-β-CD (12 equiv. with respect to Pd) to the Pd(tris(p-OMe)TPPTS)3 complex does not modify the 31 P{1 H} NMR spectrum as this ligand does not interact with the CD. In fact, even at high temperature, a broad signal at 19 ppm is detected which corresponds to the average signal of the equilibrium between the organometallic complex and free tris(p-OMe)TPPTS (Figure 10). 2.2.2. ortho-Substituted Ligands The same experiments were realized with the ortho-substituted ligands but the synthesis of the PdL3 complex failed. Indeed, Pd extraction from the organic phase to the aqueous phase is too low. The bulkiness of the hydrosoluble ortho-substituted are obviously responsible for the equilibrium displacement toward the organic Pd(TPP)4 complex. Again, these results are in accordance with the previous observations made with the platinum complexes study showing that these ligands hardly coordinate the metal centre.

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phosphane oxide Oxyde

RAM Molar ratio

RAME-β-CD Pd

25°C) 25°C)

45°C) 45°C) PdL3 + L*L* PdL 3+

PdL PdL22L* + LL

0

65°C) 65°C)

85°C) 85°C)

PdL PdL3 3

Oxyde

CD included phosphane oxide

L CD included phosphane

25°C) 25°C)

45°C) 45°C)

PdL3 +3 +L*L* PdL

PdL PdL22L* + LL

3

PdL33++L* PdL L*

PdL22L* L*++ LL PdL

12

65°C) 65°C)

85°C) 85°C) PdL PdL3

3

25°C) 25°C)

45°C) 45°C)

65°C) 65°C)

85°C) 85°C) 38 (ppm) 38 (ppm)

30 30

22 22

14 14

66

-2 -2

-10 -10

-18 -18

Figure 9. 9.3131P{ H} NMR NMRspectra spectra of Pd(tris(p-Me)TPPTS) both temperature and Figure P{11H} of Pd(tris(p-Me)TPPTS) 3 depending on bothon temperature and RAME3 depending β-CD quantity in D2O ligand concentration of 66 mM. RAME-β-CD quantity inwith D2 Oawith a ligand concentration of 66 mM.

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phosphane oxide PdL3 + L*

PdL2L* + L

PdL3 + L*

PdL2L* + L

a) a)

b) b)

c) c)

(ppm) (ppm)

38 38

34 34

30 30

26 26

22 22

18 18

14 14

10 10

66

2 2

-2 -2

-6 -6

-8

1 H} NMR spectra of Pd(tris(p-OMe)TPPTS) at (a) 25 ◦ C; (b) +12 equiv. of RAME-β-CD Figure 10. 31 P{ 3 31P{1H} NMR spectra of Pd(tris(p-OMe)TPPTS) Figure 10. 3 at (a) 25 °C; (b) +12 equiv. of RAME-β-CD at 25 ◦ C (c) +12 equiv. of RAME-β-CD at 85 ◦ C in D2 O with a ligand concentration of 66 mM. at 25 °C (c) +12 equiv. of RAME-β-CD at 85 °C in D2O with a ligand concentration of 66 mM.

2.2.3. Biphenylphosphane Ligands 2.2.3. Biphenylphosphane Ligands [Pd(0)/P(Biph)Ph2 TS] Complex [Pd(0)/P(Biph)Ph2TS] Complex In this case, comments are identical to the previous Pd(tris(p-Me)TPPTS)3 complex (see ESI). In this case, comments are identical to the previous Pd(tris(p-Me)TPPTS)3 complex (see ESI). That That is to say, CD addition to a Pd(P(Biph)Ph2 TS)3 aqueous solution reduces the chemical exchange rate is to say, CD addition to a Pd(P(Biph)Ph2TS)3 aqueous solution reduces the chemical exchange rate between free ligand and the organometallic complex. Increasing both temperature and RAME-β-CD between free ligand and the organometallic complex. Increasing both temperature and RAME-β-CD quantity do not yield to the formation of other palladium species. However, 2D NMR T-ROESY quantity do not yield to the formation of other palladium species. However, 2D NMR T-ROESY experiment of a 1:1 β-CD:Pd(P(Biph)Ph2 TS)3 mixture exhibited intense cross-peaks between the experiment of a 1:1 β-CD:Pd(P(Biph)Ph2TS)3 mixture exhibited intense cross-peaks between the phosphane aromatic protons and the internal CD protons H3 and H5 (Figure 11). The presence of phosphane aromatic protons and the internal H3 and H5 (Figure 11). The presence of only 31 P{CD 1 H} protons only 4% (determined by integration of the NMR spectrum) of free ligand which is trapped 31 1 4% (determined by integration of the P{ H} NMR spectrum) of free ligand which is trapped by the by the CD in the mixture could not be responsible for such intense cross peaks. Therefore, absence CD in the mixture could not be responsible for such intense cross peaks. Therefore, absence of new of new palladium species together with strong correlation between the CD and the ligand in the 2D palladium species together with strong correlation between the CD and the ligand in the 2D T-ROESY T-ROESY NMR spectrum enable us to assume the formation of inclusion complex between the CD and NMR spectrum enable us to assume the formation of inclusion complex between the CD and the the ligand (coordinated to the palladium centre). As with the platinum complex, the P(Biph)Ph2 TS ligand (coordinated to the palladium centre). As with the platinum complex, the P(Biph)Ph2TS ligand ligand allows the formation of organometallic palladium species where the cyclodextrin plays the role allows the formation of organometallic palladium species where the cyclodextrin plays the role of of coordination second sphere ligand. coordination second sphere ligand. Furthermore, intense cross-peaks between the CD internal H3 protons and Ha of the biphenyl Furthermore, intense cross-peaks between the CD internal H3 protons and Ha of the biphenyl moiety together with high correlations between the CD internal H5 protons and Hc /Hd of the biphenyl moiety together with high correlations between the CD internal H5 protons and Hc/Hd of the biphenyl moiety in the T-ROESY spectrum allow us to propose a geometry where the phosphane penetration in moiety in the T-ROESY spectrum allow us to propose a geometry where the phosphane penetration the CD cavity takes place via the primary face (Scheme 5). in the CD cavity takes place via the primary face (Scheme 5). It should be noted however, that this geometry differs from the geometry of the inclusion complex It should be noted however, that this geometry differs from the geometry of the inclusion between the free ligand in solution and the CD which takes place via the CD secondary face (see ESI). complex between the free ligand in solution and the CD which takes place via the CD secondary face The spatial proximity of the palladium coordinated ligands inevitably leads to a high steric hindrance (see ESI). The spatial proximity of the palladium coordinated ligands inevitably leads to a high steric which could be responsible for such a difference in the geometry. hindrance which could be responsible for such a difference in the geometry.

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Figure 11. 11. 2D (11(11 mM) and Pd(P(Biph)Ph 2TS)TS) 3 (11 Figure 2DT-ROESY T-ROESYspectrum spectrumofofaasolution solutioncontaining containingβ-CD β-CD mM) and Pd(P(Biph)Ph 2 3 Figure 11. 2D T-ROESY spectrum of a solution containing β-CD (11 mM) and Pd(P(Biph)Ph 2TS)3 (11 ◦ 2 O. mM) at 25 °C in D (11 mM) at 25 C in D2 O. mM) at 25 °C in D2O. NaO 3S NaO 3S

NaO3S NaO3S

SO3Na SO3Na

P P 2

P Pd P Pd P P

2 2

2 SO3Na SO3Na

SO3Na SO3Na

2 2

SO3Na SO3Na

Scheme 5. geometry of the organometallic palladium palladium species species where where CD plays the role of 5. Possible geometry Scheme 5. Possible of the organometallic palladium species where CD plays the role of coordination secondgeometry sphere ligand. sphere ligand. coordination second sphere ligand.

[Pd(0)/P(Biph)22PhTS] [Pd(0)/P(Biph) PhTS]Complex Complex [Pd(0)/P(Biph) 2PhTS] Complex 31 31P{ different RAME-β-CD RAME-β-CD P{11H} H} NMR NMR spectra spectra of Pd(P(Biph)22PhTS) PhTS)33 complexes complexes in in addition addition to different 31P{1H} NMR spectra of Pd(P(Biph)2PhTS)3 complexes in addition to different RAME-β-CD different temperatures temperatures are are given given in in Figure Figure12. 12. concentrations and at different concentrations and at different temperatures are given in Figure 12.

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Molar ratio

phosphane oxide

RAME-β-CD

PdL2

Pd 25°C)

40°C)

0 60°C)

85°C)

PdL3 CD included phosphane oxide

CD included phosphane

PdL2

25°C)

40°C)

3 60°C)

85°C)

25°C)

40°C)

12 60°C)

85°C) (ppm)

50

40

30

20

10

0

-10

-20

Figure 12.12.3131P{P{1 1H} complexessynthetized synthetizedwith withP(Biph) P(Biph) depending Figure H} NMR NMR spectra spectra of palladium palladium complexes 2PhTS depending 2 PhTS of of 66 66 mM. bothtemperature temperatureand andRAME-β-CD RAME-β-CD quantity quantity in onon both inD D22OOwith witha aligand ligandconcentration concentration mM.

At room temperature and without CD, two different broad signals corresponding to the PdL3 At room temperature and without CD, two different broad signals corresponding to the PdL3 and and PdL2 complexes in fast equilibrium with free ligand are observed. Neither temperature, nor PdL2 complexes in fast equilibrium with free ligand are observed. Neither temperature, nor addition of addition of 3 equiv. of RAME-β-CD do not allow to observe new organometallic species. Indeed, CD 3 equiv. of RAME-β-CD do not allow to observe new organometallic species. Indeed, CD addition only addition only leads to the apparition of the complexed free ligand at −7.5 ppm, a phosphane oxide leads to the apparition of the complexed free ligand at −7.5 ppm, a phosphane oxide chemical shift chemical shift trapped by the CD and a sharpening of the organometallic complexes signals which trapped by the CD and a sharpening of the complexes signals which are in are in equilibrium. However, addition of 12organometallic equiv. of RAME-β-CD leads to a diminution ofequilibrium. the PdL3 However, addition of 12 equiv. of RAME-β-CD leads to a diminution of the PdL3 species in favour

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species species in in favour favour of of the the PdL PdL22 species species and and free free ligand ligand trapped trapped by by the the CD. CD. On On the the other other hand, hand, temperature increase has a negligible influence on the PdL 3/PdL2 ratio. At high temperature, natural temperature increase hasfree a negligible influence on the /PdL 2 ratio. At high temperature, natural of the PdL2 species and ligand trapped by the CD.PdL On 3the other hand, temperature increase has dissociation increase PdL 3 species is probably offset by the stability diminution of the inclusion increase of ofonthe the PdL 3 species is probably offset by the stability diminution of the inclusion adissociation negligible influence the PdL /PdL ratio. At high temperature, natural dissociation increase of 3 2 complex between the CD and the phosphane. To sum up, high CD quantity is able to shift the complex between the CD and the phosphane. To sum up, high CD quantity is able to shift the the PdL3 species is probably offset by the stability diminution of the inclusion complex between equilibrium between different species of equilibrium between the theTo different palladium species towards towards the formation of low-coordinated low-coordinated CD and the phosphane. sum up,palladium high CD quantity is able tothe shiftformation the equilibrium between the species (Scheme 6). species (Scheme 6). species towards the formation of low-coordinated species (Scheme 6). different palladium

Scheme 6. between the different palladium species with P(Biph) in the Scheme 6. 6. Equilibria Equilibria palladium species species with with P(Biph) P(Biph)22PhTS PhTS as as ligand ligand in the Scheme Equilibria between between the the different different palladium ligand in the 2 PhTS as 31 1H} NMR P{ presence of 12 equiv. of RAME-β-CD toward palladium (species observed on the 31 1 P{1 H} NMR presence of of 12 12 equiv. equiv. of of RAME-β-CD RAME-β-CD toward toward palladium palladium (species (species observed observed on on the the 31 P{ presence H} NMR spectrum are presented on aa grey background). spectrum are presented on grey background). spectrum are presented on a grey background).

[Pd(0)/P(Biph) [Pd(0)/P(Biph)33TS] TS] Complex Complex [Pd(0)/P(Biph) 3 TS] Complex As already described [16], the ligand P(Biph) As already already described described [16], [16], the the ligand ligand P(Biph) P(Biph)33TS TS forms forms aa new new palladium palladium species species at at room room As 3 TS forms a new palladium species at room temperature:PdL 4 which have a chemical shift of 15 ppm. Without CD, PdL3 and PdL4 species are in temperature:PdL4 which have a chemical shift of 15 ppm. Without CD, PdL3 and PdL4 species are in temperature:PdL 4 which have a chemical shift of 15 ppm. Without CD, PdL3 and PdL4 species slow equilibrium. Indeed, when the is the signals of both complexes are slow equilibrium. Indeed, whenwhen the temperature temperature is increased, increased, thethe signals are in slow equilibrium. Indeed, the temperature is increased, signalsofofboth bothcomplexes complexes are are broadened and merge together at 85 °C (Figure 13). Moreover, the NMR spectrum carried out at room broadened and and merge merge together together at at 85 85 ◦°C carried out out at broadened C (Figure (Figure 13). 13). Moreover, Moreover, the the NMR NMR spectrum spectrum carried at room room temperature after heating gave the same signals reflecting the reversibility of the process. temperature after after heating heating gave gave the the same same signals signals reflecting reflecting the the reversibility reversibility of of the the process. process. temperature PdL PdL33

+L +L -L -L

PdL PdL44

phosphane phosphane oxide oxide

25°C) 25°C)

40°C) 40°C)

60°C) 60°C) PdL PdL33

+L +L PdL PdL44 -L -L

85°C) 85°C) (ppm) (ppm) 50 50

45 45

40 40

35 35

30 30

25 25

20 20

15 15

10 10

5 5

0 0

-5 -5

-10 -10 -15 -15 -20 -20

Figure 13. 31 P{11 H} NMR spectra of palladium complexes synthetized with P(Biph)3 TS depending on 31P{ Figure 13. NMR spectra of palladium synthetized 31P{1H} Figure 13. NMR ofconcentration palladium complexes complexes synthetized with with P(Biph) P(Biph)33TS TS depending depending on on temperature in H} D2 O withspectra a ligand of 66 mM. temperature in D 2O with a ligand concentration of 66 mM. temperature in D2O with a ligand concentration of 66 mM.

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By adding increasing amounts of RAME-β-CD, the PdL4 signal disappears concurrently with an By adding increasing amounts of RAME-β-CD, the PdL4 signal disappears concurrently with an increase of both the PdL3 signal and the free ligand trapped by the CD (Figure 14). increase of both the PdL3 signal and the free ligand trapped by the CD (Figure 14). PdL3 PdL4

CD included Ligand Molar ratio

oxide

RAME-β-CD Phosphane 0

0.2

0.4 CD included phosphane oxide

1 PdL2

4 (ppm) 50 45

40

35 30 25

20 15

10

5

0

-5

-10 -15 -20

Figure 14. 31 P{1 H} NMR spectra effect of RAME-β-CD quantity on the equilibrium of the different Figure 14. 31P{1H} NMR spectra effect of RAME-β-CD quantity on the equilibrium of the different palladium species formed with the ligand P(Biph)3 TS in D2 O at 25 ◦ C with a ligand concentration of palladium species formed with the ligand P(Biph)3TS in D2O at 25 °C with a ligand concentration of 66 mM. 66 mM.

When quantity reaches reachesfour fourequivalents equivalentsofofligand, ligand,species species PdL Similarly to When the CD quantity PdL 2 appears. Similarly to the 2 appears. the above-mentioned Pd(P(Biph) PhTS) complex, temperature has a negligible influence on the above-mentioned Pd(P(Biph) 2PhTS) 3 complex, temperature has a negligible influence on the 2 3 PdL /PdL22ratio ratiowhen when P(Biph) is used (Figure 15). Again, RAME-β-CD ablethe to equilibria shift the PdL33/PdL P(Biph) 3TS3 TS is used (Figure 15). Again, RAME-β-CD is able toisshift equilibria between the palladium different palladium organometallic species when3TS P(Biph) used as ligand. between the different organometallic species when P(Biph) is used asisligand. 3 TS A this palladium study is presented in Table 3. To sum the up, different ligands A short shortoverview overviewofof this palladium study is presented in Table 3. Toup, sum the different used in this can be classified in three categories: ligands usedstudy in this study can be classified in three categories:

(1) ligands notnot affected by the addition (TPPTS, tris(p(1) ligands forming formingpalladium palladiumcomplexes complexes affected by RAME-β-CD the RAME-β-CD addition (TPPTS, Me)TPPTS and tris(p-OMe)TPPTS) tris(p-Me)TPPTS and tris(p-OMe)TPPTS) (2) ligands complexes where where the the CD CD could could play play the the role role of of coordination coordination second second (2) ligands forming forming palladium palladium complexes sphere ligand (P(Biph)Ph 2TS) sphere ligand (P(Biph)Ph2 TS) (3) ligands forming palladium complexes which are transformed by the presence of RAME-β-CD. (3) ligands forming palladium complexes which are transformed by the presence of RAME-β-CD. Indeed, P(Biph)2PhTS and P(Biph)3TS spontaneously form respectively PdL3/PdL2 and Indeed, P(Biph)2 PhTS and P(Biph)3 TS spontaneously form respectively PdL3 /PdL2 and PdL4/PdL3 organometallic complexes which are converted in PdL2 complexes when CD is added PdL4 /PdL3 organometallic complexes which are converted in PdL2 complexes when CD is due to shift equilibria between the different organometallic species. However, formation of added due to shift equilibria between the different organometallic species. However, formation species where the CD acts as coordination second sphere ligand could not be avoided as the of species where the CD acts as coordination second sphere ligand could not be avoided as the biphenyl moiety is well recognised by its cavity. In these cases, the organometallic complexes biphenyl moiety is well recognised by its cavity. In these cases, the organometallic complexes formed would naturally evolve to low-coordinated species through steric decompression by formed would naturally evolve to low-coordinated species through steric decompression by ligand decoordination. ligand decoordination.

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PdL3 CD included phosphane oxide CD included phosphane oxide

CD included Ligand CD included Ligand

PdL3

PdL2

PdL2

25°C) 25°C)

40°C) 40°C)

60°C) 60°C)

85°C) (ppm) 85°C) 50 45 (ppm) 50

40

35

45

40

30 35

25 30

20

15

25

20

10 15

5 10

0

-5 5

0

-10 -5

-15 -10

-20 -15

-20

Figure 15. 31 P{1 H} NMR spectra of palladium complexes synthetized with P(Biph)3 TS depending on Figure 15. 31P{1H} NMR spectra of palladium complexes synthetized with P(Biph)3TS depending on temperature in the presence of 4 equiv. of RAME-β-CD towards the phosphane in D2 O with a ligand 31 presence 1H} NMR temperature the of spectra 4 equiv.ofofpalladium RAME-β-CD towardssynthetized the phosphane D2O with ligand Figurein 15. complexes withinP(Biph) 3TS a depending on concentration of 66P{mM. concentration of 66 mM. temperature in the presence of 4 equiv. of RAME-β-CD towards the phosphane in D2O with a ligand

of 66 mM. species observed after RAME-β-CD addition (1 to 12 equiv. toward Table concentration 3. New organometallic Table 3. New organometallic species observed after RAME-β-CD addition (1 to 12 equiv. toward palladium) to a solution of the palladium complexes formed by extraction with an aqueous ligand palladium) to3.aNew solution of the palladium complexes by extraction with an(1aqueous ligandtoward Table organometallic species observedformed after RAME-β-CD addition to 12 equiv. solution (66 mM). solution (66 mM). to a solution of the palladium complexes formed by extraction with an aqueous ligand palladium) solution (66 mM). Palladium Complex New Species Obtained Palladium Complex New Species Obtained Ligand Ligand Obtained without CD after RAME-β-CD after RAME-β-CD Addition Obtained without CD Addition Palladium Complex New Species Obtained Ligand TPPTS PdL 3 TPPTS PdL Obtained after RAME-β-CD Addition 3 without CD tris(p-Me)TPPTS PdL 3 TPPTS PdL 3 tris(p-Me)TPPTS PdL3 tris(p-OMe)TPPTS PdL3 PdL3 tris(p-Me)TPPTS tris(p-OMe)TPPTS PdL3 tris(o-Me)TPPTS No palladium extraction tris(p-OMe)TPPTS PdL3 tris(o-Me)TPPTS palladium extraction tris(o-OMe)TPPTS NoNo palladium extraction tris(o-Me)TPPTS No palladium extraction tris(o-OMe)TPPTS No palladium extraction -tris(o-OMe)TPPTS No palladium extraction P(Biph)Ph2TS 2TS P(Biph)PhP(Biph)Ph 2 TS

PdL3 PdL3PdL3

P(Biph)2PhTS PdL3 + PdL2 [PdL2] increase P(Biph) 3TS PdL 4 + PdL3 [PdL 3] increase + PdL2 formed P(Biph)2PhTS 3 + PdL2 [PdL2]] increase increase P(Biph)2 PhTS PdL3PdL + PdL [PdL 2 2 P(Biph)3TS PdL4 + PdL3 [PdL3] increase + PdL2 formed [PdL 3 TS 4 + PdL3and Platinum 3 ] increase + PdL2 formed 2.3. ComparisonP(Biph) of the Results Obtained withPdL Palladium Complexes

2.3.overview Comparison of the Results Obtained with Palladium An of the results is presented in Table 4. and Platinum Complexes 2.3. Comparison of the Results Obtained with Palladium and Platinum Complexes An overview of the results is presented in Table 4. An overview of the results is presented in Table 4.

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Table 4. Effects of RAME-β-CD addition on the platinum and palladium complexes obtained with the different phosphanes (in D2 O, at 25 ◦ C); CD = RAME-β-CD; L@CD = Ligand included in the CD cavity. Entry

Ligand (L)

Influence of CD on Pt Complexes

Influence of CD on Pd Complexes

1

TPPTS

[PtL3 Cl]Cl + CD → cis-PtCl2 L2 + L@CD CD = decoordination promotor

2

tris(p-Me)TPPTS tris(p-OMe)TPPTS

[PtL3 Cl]Cl unchanged with CD

PdL3 unchanged with CD

3

tris(o-Me)TPPTS tris(o-OMe)TPPTS

[PtL3 Cl]Cl impossible to obtain; trans-PtCl2 L2 was formed with or without CD

Ligand unable to extract Pd from the organic layer with or without CD

4

P(Biph)Ph2 TS

[PtL3 Cl]Cl + CD → [(L@CD)PtL2 Cl]Cl CD = second sphere ligand

PdL3 + CD → (L@CD)PdL2 CD = second sphere ligand

n.d. (broad signals with or without CD)

PdL3 + CD → PdL*2 + L@CD L* = L or L@CD CD = decoordination promotor and second sphere ligand

n.d. (broad signals with or without CD)

PdL4 + CD → PdL*3 + L@CD PdL*3 + CD → PdL*2 + L@CD L* = L or L@CD CD = decoordination promotor and second sphere ligand

5

6

P(Biph)2 PhTS

P(Biph)3 TS

PdL3 unchanged with CD

Firstly, tris-ortho-substituted hydrosoluble phosphanes led to low coordinated platinum species and are unable to extract palladium from a Pd(TPP)4 toluene solution (Table 4, entry 3). These two behaviours are probably due to the steric hindrance around their phosphorous atom making them poor ligands. Apart from this peculiar case and the results obtained with platinum for P(Biph)2 PhTS and P(Biph)3 TS ligands (broad signals in 31 P{1 H} NMR) (entries 5 and 6), three CD behaviours towards [PtL3 Cl]Cl and PdLn complexes were noticed:

•

•

•

The CD can have no influence on the organometallic species. That is what is observed with para-substituted hydrosoluble phosphanes for both palladium and platinum complexes (entry 2) and also with TPPTS, only in the case of palladium (entry 1). For the para-substituted hydrosoluble phosphanes, this behaviour could be explained by the lack of interaction between the CD and the phosphane (tris(p-OMe)TPPTS), or by a too strong metal-phosphorus bond coming from a high σ-donor ligand (tris(p-Me)TPPTS). However, the fact that the PdL2 species is not formed after CD addition on the PdL3 complex not only for tris(p-OMe)TPPTS and tris(p-Me)TPPTS but also for TPPTS probably comes from the too unstable PdL2 (14e− species) in the case of TPPTS derivatives. The CD can act as a phosphane decoordination promotor. This property was emphasised with TPPTS as ligand in the [PtL3 Cl]Cl complex (entry 1), and with P(Biph)2 PhTS and P(Biph)3 TS ligands in the case of PdLn type complexes (entries 5 and 6). The fact that TPPTS can be removed from Pt by addition of CD, contrary to tris(p-OMe)TPPTS and tris(p-Me)TPPTS, comes not only from its ability to be included in the CD cavity but also to its lower coordination power (less basic ligand). The CD can act as a second sphere ligand by including the metal-bound phosphane. This property was undoubtedly highlighted for both platinum and palladium complexes with the P(Biph)Ph2 TS ligand whose p-sodiosulfobiphenyl group is well recognized by the CD. Because of this identical group present in their structure, making them accessible for a cyclodextrin even when bound to a metal, it is also important to say that P(Biph)2 PhTS and P(Biph)3 TS based organometallic species form also surely supramolecular complexes with CD. This property plays probably a role in the observed decoordination of P(Biph)2 PhTS and P(Biph)3 TS from palladium, the CD being able to stabilize the low-coordinated resulting organometallic species. More concretely, this property can explain the observation of PdL2 type species when P(Biph)3 TS ligand was used, species not formed with TPPTS ligand. Indeed, TPPTS structure doesn’t permit complexation when bound to the metal.

Molecules 2017, 22, 140 

21 of 25 

The three evoked behaviours of CD in the presence of a phosphane bound to a metal depend on  different equilibria whose evolution is assumed to be under thermodynamic control. Indeed, in all  the  experiments  conducted  in  this  study,  the  temperature  had  always  a  reversible  effect  on  the  Molecules 2017, 22, 140 21 of 25 system.  More  concretely,  the  modification  of  spectra  sometimes  observed  by  heating 21 of 25  disappeared  Molecules 2017, 22, 140  systematically by recovering the room temperature.  The three evoked behaviours of CD in the presence of a phosphane bound to a metal depend Basically, by considering a simplified system consisting of a cyclodextrin (CD) and a phosphane  The three evoked behaviours of CD in the presence of a phosphane bound to a metal depend on  on different equilibria whose evolution is assumed to be under thermodynamic control. Indeed, in (L ligand) coordinated to a metal (Met), i.e., a “Met ← L + CD” system, several evolutions are possible.  different equilibria whose evolution is assumed to be under thermodynamic control. Indeed, in all  Firstly, the phosphane can naturally leave the metal by decoordination and lead to a “Met + L + CD”  all experiments conducted this study,the  thetemperature  temperaturehad  hadalways  alwaysa a reversible  reversible effect  effect on  on the the the experiments  conducted  in  in this  study,  the  system. More concretely,  concretely, the system. system (Scheme 7a, 1). This last system can then be transformed by inclusion of the free ligand in the  More  the  modification modification  of of  spectra spectra  sometimes sometimes  observed observed  by by heating heating disappeared disappeared  CD cavity (Scheme 7a, 2). Starting from the same initial system (“Met ← L + CD”), another evolution  systematically by recovering the room temperature. systematically by recovering the room temperature.  can be the complexation of ligand bound to the metal to reach a “Met ← L@CD” system in which the  Basically, by considering a simplified system consisting of a cyclodextrin (CD) and a phosphane Basically, by considering a simplified system consisting of a cyclodextrin (CD) and a phosphane  CD acts as a second sphere ligand (Scheme 7a, 3). In this complex, the “L@CD” part constitutes a  (L ligand) coordinated to a metal (Met), i.e., a “Met ← L + CD” system, several evolutions are possible. (L ligand) coordinated to a metal (Met), i.e., a “Met ← L + CD” system, several evolutions are possible.  Molecules 2017, 22, 140  21 of 25  supramolecular ligand which can therefore also leave the metal to lead to a “Met + L@CD” system  Firstly, the phosphane can naturally leave the metal by decoordination and lead to a “Met + L + CD”  Firstly, the phosphane can naturally leave the metal by decoordination and lead to a “Met + L + CD” (Scheme  7a, 1).4).  The  are  in byequilibrium  their  proportions  are  system (Scheme 7a, 1). This last system can then be transformed by inclusion of the free ligand in the  system (Scheme 7a, This lastfore‐mentioned  system can then systems  be transformed inclusion of and  the free ligand in the The three evoked behaviours of CD in the presence of a phosphane bound to a metal depend on  21 of 25  consequently driven by their free enthalpy, the more stable system being the more represented one.  CD cavity (Scheme 7a, 2). Starting from the same initial system (“Met ← L + CD”), another evolution  CD cavity (Scheme 7a, 2).21 of 25  Starting from the same initial system (“Met ← L + CD”), another evolution different equilibria whose evolution is assumed to be under thermodynamic control. Indeed, in all  So, when the “Met ← L” starting organometallic species stays perfectly stable in the presence of  can be the complexation of ligand bound to the metal to reach a “Met ← L@CD” system in which the  can be the in  complexation of ligand bound to thealways  metal to reach a “Met ← L@CD” he  experiments  conducted  this  study,  the  temperature  had  a  reversible  effect  on  the  system in which a phosphane bound to a metal depend on  L + CD” system is very low compared to the other  CD acts as a second sphere ligand (Scheme 7a, 3). In this complex, the “L@CD” part constitutes a  the CDCD, it means that the free enthalpy of the “Met ← acts as a second sphere ligand (Scheme observed  7a, 3). In this complex, the “L@CD” part constitutes ystem.  More  concretely,  the  modification  of  spectra  sometimes  by  heating  disappeared  er thermodynamic control. Indeed, in all  ence of a phosphane bound to a metal depend on  possible  (Scheme  Different  can  produce  basicity system of  the  ligand  asupramolecular ligand which can therefore also leave the metal to lead to a “Met + L@CD” system  supramolecular ligand can7b).  therefore alsoreasons  leave the metal to leadthis  to asituation:  “Met + L@CD” ystematically by recovering the room temperature.  e  had  always  a  reversible  effect  systems  on  the  which  be under thermodynamic control. Indeed, in all  (Scheme  7a,  The  fore‐mentioned  systems  are  in  equilibrium  and  their  are proportions  are  (Scheme 7a, 4).4).  Theeffect  fore-mentioned systems are in equilibrium and their proportions consequently Basically, by considering a simplified system consisting of a cyclodextrin (CD) and a phosphane  etimes  observed  by  heating  disappeared  mperature  had  always  a  making the “Met ← reversible  on L” bond very strong, ligand poorly recognized by the CD...  the  In the same way, when CD is proved to be a decoordination promotor by being able to do an  consequently driven by their free enthalpy, the more stable system being the more represented one.  driven by their freedisappeared  enthalpy, the more stable system being the more represented one. L ligand) coordinated to a metal (Met), i.e., a “Met ← L + CD” system, several evolutions are possible.  tra  sometimes  observed  by  heating  So, when the “Met ← Firstly, the phosphane can naturally leave the metal by decoordination and lead to a “Met + L + CD”  So,inclusion complex with the phosphane, it means that the “Met + L@CD” system is relatively close to  when the “Met ←L” starting organometallic species stays perfectly stable in the presence of  L” starting organometallic species stays perfectly stable in the presence g of a cyclodextrin (CD) and a phosphane  .  CD, it means that the free enthalpy of the “Met ← ystem (Scheme 7a, 1). This last system can then be transformed by inclusion of the free ligand in the  of CD, the “Met ← it means thatL + CD” initial system, in terms of free enthalpy (Scheme 7(c)). In this case, the “Met +  the free enthalpy of the “MetL + CD” system is very low compared to the other  ← L + CD” system is very low compared to the D” system, several evolutions are possible.  onsisting of a cyclodextrin (CD) and a phosphane  L@CD” system can be reached either by preliminary natural decoordination of the phosphane via the  possible  systems  (Scheme  7b). 7b). Different  reasons  can can produce  this  CD cavity (Scheme 7a, 2). Starting from the same initial system (“Met ← L + CD”), another evolution  ordination and lead to a “Met + L + CD”  other possible systems (Scheme Different reasons produce thissituation:  situation:basicity  basicityof  of the  the ligand  ligand ← L + CD” system, several evolutions are possible.  “Met  +  L  CD”  system  (Scheme  7(c)),  mechanism  with  steps  1  and  2)  or  by  making the “Met ← an be the complexation of ligand bound to the metal to reach a “Met ← L@CD” system in which the  med by inclusion of the free ligand in the   by decoordination and lead to a “Met + L + CD”  making the “Met ←+ L” bond very strong, ligand poorly recognized by the CD...  L” bond very strong, ligand poorly recognized bythe  thesuccessive  CD... complexation of  the  organometallic  species  by promotor the  CD  (Scheme 7(c),  In the same way, when CD is proved to be a decoordination promotor by being able to do an  CD acts as a second sphere ligand (Scheme 7a, 3). In this complex, the “L@CD” part constitutes a  em (“Met ← L + CD”), another evolution  transformed by inclusion of the free ligand in the  In preliminary  the same way, when CD is proved to be a decoordination by being ablemechanism with  to do an steps  3  and  4  successively).  This  second  mechanism  is  probably  favoured  when  the  is  able  to  inclusion complex with the phosphane, it means that the “Met + L@CD” system is relatively close to  upramolecular ligand which can therefore also leave the metal to lead to a “Met + L@CD” system  ch a “Met ← L@CD” system in which the  itial system (“Met ← L + CD”), another evolution  inclusion complex with the phosphane, it means that the “Met + L@CD” system is relativelyCD  close include  bound  to in  the equilibrium  metal,  i.e.,  the  free  enthalpy 7(c)). of  the InMet  L@CD  the “Met ← L + CD” initial system, in terms of free enthalpy (Scheme 7(c)). In this case, the “Met +  Scheme  7a,  4).  to The  fore‐mentioned  systems  are  and enthalpy their  proportions  are  complex, the “L@CD” part constitutes a  al to reach a “Met ← L@CD” system in which the  the “Met ← the  L +ligand  CD” initial system, in terms of when  free (Scheme this←case, the is  low.  [PtLdecoordination 3Cl]Cl species by CD proceed via the “1,  L@CD” system can be reached either by preliminary natural decoordination of the phosphane via the  onsequently driven by their free enthalpy, the more stable system being the more represented one.  metal to lead to a “Met + L@CD” system   In this complex, the “L@CD” part constitutes a  “Met +Therefore, one can think that TPPTS decoordination from  L@CD” system can be reached either by preliminary natural of the phosphane 2 “ mechanism  (Met ← L@CD species is too high in free enthalpy to be easily reached in the case of  “Met  +  L  +  + CD”  (Scheme  7(c)), 7(c)), mechanism  with  the the successive  steps  1  1and  So, when the “Met ← L” starting organometallic species stays perfectly stable in the presence of  equilibrium  and  via their  are  ve the metal to lead to a “Met + L@CD” system  theproportions  “Met L + system  CD” system (Scheme mechanism with successive steps and2)  2) or  or by  by preliminary  complexation of  the  organometallic  species  by  the  (Scheme 7(c),  mechanism with  CD, it means that the free enthalpy of the “Met ← L + CD” system is very low compared to the other   system being the more represented one.  re  in  equilibrium  and TPPTS) and that biphenyl phosphanes decoordination from palladium species proceed by the “3, 4”  their  proportions  preliminary complexation of are  the organometallic species by the CD CD  (Scheme 7(c), mechanism with steps L@CD is easy to form).  and  successively).  This  second  mechanism  is  probably  favoured  when  the  CD  is  able the to  possible  systems  (Scheme  7b). 4 Different  reasons  can  produce  this  situation:  basicity  of  the  es stays perfectly stable in the presence of  e stable system being the more represented one.  3steps  and 3  4 mechanism (Met ← successively). This second mechanism is probably favoured when theligand  CD is able to include L@CD” species can be obtained from the initial “Met ← L + CD” system via  include  the Finally, the “Met ← ligand  to  the  metal,  i.e., enthalpy when  the  enthalpy  of  the  Met Therefore, ← L@CD  is  low.  making the “Met ← L” bond very strong, ligand poorly recognized by the CD...  system is very low compared to the other  ic species stays perfectly stable in the presence of  ligand bound to the bound  metal, i.e., when the free of free  the Met ← L@CD is low. one can direct  complexation  (scheme  7(d),  3)  or  via  preliminary  formation  of  the  “L@CD”  inclusion  Therefore, one can think that TPPTS decoordination from  [PtL 3 Cl]Cl  species by CD proceed via the “1,  In the same way, when CD is proved to be a decoordination promotor by being able to do an  uce  this  situation:  basicity  of  the  ligand   + CD” system is very low compared to the other  think that TPPTS decoordination from [PtLstep  Cl]Cl species by CD proceed via the “1, 2 “ mechanism 3 complex in solution (Scheme 7(d), steps 1, 2 and ‐4).  2 “ mechanism  ( Met ← L@CD species is too high in free enthalpy to be easily reached in the case of  nclusion complex with the phosphane, it means that the “Met + L@CD” system is relatively close to  ognized by the CD...  an  produce  this  situation:  basicity  of  the  ligand  (Met ← L@CD species is too high in free enthalpy to be easily reached in the case of TPPTS) and The simple rationalization of the different transformations observed in this study for platinum  TPPTS) and that biphenyl phosphanes decoordination from palladium species proceed by the “3, 4”  he “Met ← L + CD” initial system, in terms of free enthalpy (Scheme 7(c)). In this case, the “Met +  ination promotor by being able to do an  orly recognized by the CD...  that biphenyl phosphanes decoordination from palladium species proceed by the “3, 4” mechanism mechanism (Met ← L@CD is easy to form).  L@CD” system can be reached either by preliminary natural decoordination of the phosphane via the  Met + L@CD” system is relatively close to  decoordination promotor by being able to do an  (Met ←and palladium complexes in the presence of RAME‐β‐CD can be refined by taking into account the  L@CD is easy to form). fact that several ligands are systematically present on the metal. In particular, for ligands allowing a  Finally, the “Met ← L + CD” system via  “Met  +  L  +  CD”  system  (Scheme  7(c)),  mechanism  with  the  steps the 1  and  or  by  y (Scheme 7(c)). In this case, the “Met +  at the “Met + L@CD” system is relatively close to  Finally, the “Met ← L@CD” species can be obtained from the initial “Met ← L@CD” species can besuccessive  obtained from initial2) “Met ← L + CD” system complexation by CD when coordinated to the metal (biphenyl phosphanes, in this study), relatively  direct  complexation  (scheme  7(d),  step  3) the  or or via  preliminary  of  “L@CD”  inclusion inclusion  preliminary  complexation of  the  organometallic  species  by  CD  mechanism with   decoordination of the phosphane via the   enthalpy (Scheme 7(c)). In this case, the “Met +  via direct complexation (scheme 7(d), step 3) via(Scheme 7(c),  preliminaryformation  formation of the  the “L@CD” organometallic  species  possessing  of CD  coordination  complex in solution (Scheme 7(d), steps 1, 2 and ‐4).  teps  3  successive  and  4  successively).  This  second  is  probably  when  the  is  able  to  (phosphane  and  CD,  th  the  steps  stable  1  in and  2)  or  (Scheme by mechanism  y natural decoordination of the phosphane via the  complex solution 7(d), steps 1, 2 and favoured  -4). two  spheres  respectively)  be  obtained.  However,  in of  these  species,  the  steric  hindrance  The simple rationalization of the different transformations observed in this study for platinum  nclude  the  ligand  bound  to  the 1 metal,  i.e.,  when  enthalpy  the  Met  ← L@CD  is this low.  y  the with  CD  (Scheme 7(c),  mechanism with  ism  the  successive  steps  and may  2)  or  by  The simple rationalization ofthe  the free  different transformations observed in study forgenerated  platinum by  the  complexation  by  the  CD presence constitutes  a  possible  reason  the  included  and palladium complexes in the presence of RAME‐β‐CD can be refined by taking into account the  Therefore, one can think that TPPTS decoordination from  [PtLof 3Cl]Cl  species by CD proceed via the “1,  obably by  favoured  the  CD  is  able  to  pecies  the  CD when  (Scheme 7(c),  mechanism with  and palladium complexes in the RAME-β-CD can beexplaining  refined by that  taking into accountligand  the or  a  neighbour ligand can be expulsed to reach a more stable system (Scheme 8, pathway (a)).  fact that several ligands are systematically present on the metal. In particular, for ligands allowing a  2 “ mechanism  (favoured  Met ← L@CD species is too high in free enthalpy to be easily reached in the case of  e  of  the  Met  ← L@CD  is  low.  m enthalpy  is  probably  when  the  CD  is  able  to  fact that several ligands are systematically present on the metal. In particular, for ligands allowing Conversely, for ligands not accessible for a CD when bound to a metal (TPPTS, in this study),  TPPTS) and that biphenyl phosphanes decoordination from palladium species proceed by the “3, 4”  3Cl]Cl  species by CD proceed via the “1,   tLthe  free  enthalpy  of  the  Met  ←by L@CD  is  low.  acomplexation by CD when coordinated to the metal (biphenyl phosphanes, in this study), relatively  complexation CD when coordinated to the metal (biphenyl phosphanes, in this study), relatively the  only  way species to species  explain  an  observed  decoordination  in  the  presence  of  CD  undoubtedly  the  stable  organometallic  possessing  two  spheres  of  coordination  (phosphane  and  CD,  mechanism (Met ← L@CD is easy to form).  thalpy to be easily reached in the case of   from [PtL3Cl]Cl species by CD proceed via the “1,  stable organometallic possessing two spheres of coordination (phosphane and CD, is  respectively) preliminary decoordination of the ligand from the metal (Scheme 8, pathway (b)).  respectively)  may However, be  obtained.  However,  in the these  species,  the  steric  hindrance  by  the  Finally, the “Met ← L + CD” system via  m palladium species proceed by the “3, 4”  n free enthalpy to be easily reached in the case of  may beL@CD” species can be obtained from the initial “Met ← obtained. in these species, steric hindrance generated by thegenerated  complexation by complexation  by step  the  CD  constitutes  a  possible  reason  that  the  included ligand ligand  or bea  direct  complexation  (scheme  7(d),  3)  or  via  preliminary  formation  of explaining  the  “L@CD”  inclusion  ion from palladium species proceed by the “3, 4”  the CD constitutes a possible reason explaining that the included ligand or a neighbour can neighbour ligand can be expulsed to reach a more stable system (Scheme 8, pathway (a)).  omplex in solution (Scheme 7(d), steps 1, 2 and ‐4).  om the initial “Met ← L + CD” system via  expulsed to reach a more stable system (Scheme 8, pathway (a)). Conversely, for ligands not accessible for a CD when bound to a metal (TPPTS, in this study),  ary  The simple rationalization of the different transformations observed in this study for platinum  formation  of  the  “L@CD”  inclusion  ained from the initial “Met ← L + CD” system via  Conversely, for ligands not accessible for a CD when bound to a metal (TPPTS, in this study), the the  only  way  to  explain  an  observed  decoordination  in  the  of presence  of  CD  is  undoubtedly  the  and palladium complexes in the presence of RAME‐β‐CD can be refined by taking into account the  preliminary  formation  of  the  “L@CD”  only way to explain aninclusion  observed decoordination in the presence CD is undoubtedly the preliminary preliminary decoordination of the ligand from the metal (Scheme 8, pathway (b)).  ions observed in this study for platinum  . act that several ligands are systematically present on the metal. In particular, for ligands allowing a  decoordination of the ligand from the metal (Scheme 8, pathway (b)). omplexation by CD when coordinated to the metal (biphenyl phosphanes, in this study), relatively  can be refined by taking into account the  nsformations observed in this study for platinum  table  organometallic  species  possessing  two  spheres  of  coordination  (phosphane  and  CD,  metal. In particular, for ligands allowing a  E‐β‐CD can be refined by taking into account the  espectively)  may  be  obtained.  However,  in  these  species,  the  steric  hindrance  generated  by  the  nyl phosphanes, in this study), relatively  on the metal. In particular, for ligands allowing a  omplexation  by  the  CD  constitutes  a  possible  reason  explaining  that  the  included  ligand  or  a  of  coordination  (phosphane  and  CD,  l (biphenyl phosphanes, in this study), relatively  neighbour ligand can be expulsed to reach a more stable system (Scheme 8, pathway (a)).  s,  the  steric  hindrance  generated  by  the  pheres  of  coordination  (phosphane  and  CD,  Conversely, for ligands not accessible for a CD when bound to a metal (TPPTS, in this study),  xplaining  that steric  the  included  ligand  or  a  by  the    species,  the  hindrance  generated  he  only  way  to  explain  an  observed  decoordination  in  the  presence  of  CD  is  undoubtedly  the  stem (Scheme 8, pathway (a)).  eason  explaining  that  the  included  ligand  or  a  preliminary decoordination of the ligand from the metal (Scheme 8, pathway (b)).  bound to a metal (TPPTS, in this study),  table system (Scheme 8, pathway (a)).  the  presence  of  CD  is  undoubtedly  the  D when bound to a metal (TPPTS, in this study),  cheme 8, pathway (b)).  tion  in  the  presence  of  CD  is  undoubtedly  the  metal (Scheme 8, pathway (b)). 

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Scheme 7.7. Different possible mechanisms for the cyclodextrin cyclodextrin assisted of generation of new new Scheme Different possible mechanisms for the assisted generation of Scheme 7. Different possible mechanisms for the cyclodextrin assisted generation new organometallic organometallic species from a metal coordinated by a ligand (Met ← L species); Met = metal, organometallic species from a metal by a←ligand (Met ←Met L species); Met LL== species from a metal coordinated by coordinated a ligand (Met L species); = metal, L == metal, Phosphane, Phosphane, L@CD = ligand included in the CD cavity. Phosphane, = ligand included in the CD cavity. L@CD = ligandL@CD included in the CD cavity.

L@CD L@CD Met Met L L

Pathway Pathway(a) (a)

STARTING STARTINGSYSTEM SYSTEM 

Met Met

LL LL

L@CD L@CD Met Met L@CD L@CD

MetL@CD MetL@CD +L

Growing Growing Sterichindrance hindrance Steric

MetL@CD MetL@CD L@CD ++ L@CD

 FINAL FINALSYSTEM SYSTEM  (Biphenylphosphanestype typeligand) ligand) (Biphenylphosphanes

Pathway(b) (b) Pathway MetL ++ LL MetL

MetL + L@CD

  FINAL FINALSYSTEM SYSTEM (TPPTS (TPPTS type typeligand) ligand)

Scheme 8.8.8. Two possible coordinated organometallicspecies species thanks Scheme Two possiblepathways pathwaysof ofgeneration generation of of low thanks tototo Scheme Two possible pathways of generation of low coordinated coordinated organometallic organometallic species thanks a cyclodextrin from a species bearing several ligands (symbolized by “MetL ”): (a) via supramolecular 2 ”): (a) via supramolecular a cyclodextrin from a species bearing several ligands (symbolized by “MetL 2 a cyclodextrin from a species bearing several ligands (symbolized by “MetL2”): (a) via supramolecular organometallic species; of aaa ligand; ligand;Met Met===metal, metal,LLL=== Phosphane, organometallic species;(b) (b)via viapreliminary preliminarydecoordination decoordination of Phosphane, organometallic species; (b) via preliminary decoordination of ligand; Met metal, Phosphane, L@CD = ligand included in the CD cavity. L@CD = ligand included in the CD cavity. L@CD = ligand included in the CD cavity.

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3. Materials and Methods 3.1. General Remarks The 1 H and 31 P{1 H} NMR spectra were recorded on an Avance 300 DPX instrument (Bruker, Karlsruhe, Germany) at 300.13 and 121.49 MHz, respectively. Organic compounds were purchased from Fisher Scientific (Pittsburgh, PA, USA) in their highest purity and used without further purification. Potassium tetrachloroplatinate(II) and tetrakis(triphenylphosphane)palladium(0) were purchased from Strem Chemicals (Newburyport, MA, USA). Ultrapure water was used in all experiments (Fresenius Kabi, Bad Homburg, Germany; γ = 72.0 mN.m−1 at 25 ◦ C). Pharmaceutical grade RAME-β-CD (Cavasol® W7 M) was purchased from Wacker Chemie GmbH (München, Germany) and was used as received. Randomly methylated β-cyclodextrin (RAME-β-CD) is a partially methylated cyclodextrin and its degree of substitution was equal to 1.8 (1.8 methyl groups per glucopyranose unit). TPPTS [24], tris(o-Me)TPPTS [25], tris(o-OMe)TPPTS [25], tris(p-Me)TPPTS [15] and tris(p-OMe)TPPTS [26], P(Biph)Ph2 TS [16], P(Biph)2 PhTS [16] and P(Biph)3 TS [16] were prepared as reported in the literature. The purity of these water-soluble phosphanes was controlled by 1 H, 13 C{1 H} and 31 P{1 H} NMR analysis. 3.2.

31 P{1 H}

NMR Study on Platinum and Palladium Complexes

Platinum complexes were synthetized by dissolving K2 PtCl4 (8.3 mg, 0.02 mmol) in degassed deuterated water (2 mL). Three equiv. of the corresponding ligand (0.06 mmol) were added to the solution, which was then stirred for 15 min at room temperature under nitrogen. Studies in the presence of RAME-β-CD were conducted as follows: the required amount of cyclodextrin was introduced into 500 µL of the above solution. After 15 min of stirring, the solution was transferred into a NMR tube and analysed. Palladium complexes were synthetized according to a modified literature procedure [27]. Pd(PPh3 )4 (103 mg, 0.089 mmol.) was dissolved in 2 g of degassed toluene into a Schlenk tube under nitrogen. The corresponding phosphane (1.5 equiv., 0.133 mmol) was dissolved in 2 g of D2 O and cannulated onto the palladium solution. The mixture was stirred for 30 min at room temperature. After decantation, the organic phase was removed and a new degassed Pd(PPh3 )4 solution was added to the previous aqueous solution which underwent again a 30 min stirring period to ensure an optimal extraction of the palladium by the hydrosoluble ligand. After decantation, the aqueous phase was recovered. The obtained PdLn (n = 2, 3 or 4) solution was then used for the 31 P{1 H} NMR study. The previous solution usually contained a small excess of free ligand. Study in the presence of RAME-β-CD was conducted as follow: to 1 mL of the above solution was introduced under nitrogen the required amount of RAME-β-CD. After 15 min of stirring, the solution was transferred via cannula into a nitrogen pressurized 5 mm NMR tube. 4. Conclusions A 31 P{1 H} NMR study of platinum(II) and palladium(0) complexes coordinated with two different groups of hydrosoluble monodentate phosphane ligands (including TPPTS, meta-trisulfonated triphenylphosphane derivatives bearing one methyl (or methoxy) group on the aromatic ring and trisulfonated biphenylphosphanes) has been described. The effect of randomly methylated β-cyclodextrin (RAME-β-CD) addition on these complexes has been examined. It has been shown that the interaction of the free phosphane with RAME-β-CD is a prerequisite to observe any effect of the CD on the organometallic species (case of tris(p-OMe)TPPTS: no interaction, thus no effect). However, the stereoelectronic properties of the ligand are also of great importance. On the one hand, ligands whose phosphorous atom is hindered by ortho-substituted meta-sulfophenyl groups lead, without CD, to low coordinated organometallic species, even with an excess of ligand; the lack of free volume in the coordination sphere of these species doesn’t permit the coordination of another ligand (case of tris(o-Me)TPPTS and tris(o-OMe)TPPTS, with platinum). On the other hand,

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a high σ-donating ligand can be difficult to be removed from the metal by CD because of the stability of its metal-phosphorous bond (case of tris(p-Me)TPPTS, with platinum as well as palladium). More generally, two interesting behaviours of CD have been highlighted: the CD can act as a second sphere ligand by including the metal-bound phosphane without denaturing the organometallic species or as a phosphane decoordination promotor. These two behaviours are under thermodynamic control. Depending on the used ligand structure, the decoordination observed in the presence of CD may proceed either via a preliminary decoordination of the phosphane followed by a complexation of the free ligand by the CD (case of TPPTS) or via the generation of organometallic species complexed by CD which then lead to expulsion of ligands to decrease their internal steric hindrance (cases of biphenylphosphanes). Such modifications of organometallic complexes by a CD, i.e., inclusion of organometallic species into the cyclodextrin cavity by one of its ligand or decoordination of a ligand from the metal, can be efficient strategies to obtain new catalysts possessing original activities and selectivities. Supplementary Materials: The following are available online at http://www.mdpi.com/1420-3049/22/1/140/s1: Figures S1–S12. Acknowledgments: This work was supported by the Centre National de la Recherche Scientifique (CNRS). M. Ferreira is grateful to the Ministère de l’Education et de la Recherche for financial support (2005–2008). Author Contributions: M.F. performed the experiments; M.F., H.B., S.T. and E.M. analyzed the data and wrote the paper. Conflicts of Interest: The authors declare no conflict of interest.

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Sample Availability: Samples of the water-soluble phosphanes are available from the authors. © 2017 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).