Crystal structure and spectral characterization of

CEJC 2(3) 2004 534–552

Crystal structure and spectral characterization of dimethylthallium (III) complexes with 2-mercaptonicotinic acid and esters Monica Toma1∗ , Agust´ın Sánchez2 , Mar´ıa S. Garc´ıa–Tasende2, José S. Casas2 , José Sordo2 , Eduardo E. Castellano3 , Javier Ellena3 1

2

Department of Inorganic Chemistry, “Alexandru Ioan Cuza” University, RO-700506, Iasi, Romania Department of Inorganic Chemistry, University of Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain 3 S˜ ao Carlos Institute of Physics, University of S˜ ao Paulo, 13560 S˜ ao Carlos, SP, Brazil

Received 14 April 2004; accepted 27 May 2004 Abstract: Synthesis, spectral properties and crystal structure of dimethylthallium(III) complexes with 2-mercaptonicotinic acid (2mna), 2-mercapto-methyl-nicotinate (2mmn), 2-mercapto-ethyl-nicotinate (2men) and 2-mercapto-isopropyl-nicotinate (2min) are reported. The compounds were characterized using IR, multinuclear NMR (1 H, 13 C, 205 Tl) and mass spectrometry (electrospray, ES-API). The molecular structures of [TlMe2 (2mna)]·H2 O, (1), [TlMe2 (2mmn)], (2), [TlMe2 (2men)], (3) and [TlMe2 (2min)], (4) were determined by the single-crystal X-ray diffraction. In 1, the monodeprotonated O,S-bidentate ligand chelates one dimethylthallium(III) unit and simultaneously bridges (O and S) between two of these organometallic units. The Tl-O1’ and Tl-S” interactions are leading to polymeric chain linked in a three-dimensional network by the hydrogen bonds formed between the water molecule and the oxygen O(2) atom of the acid. The thallium atom is in a distorted octahedral environment with a [TlC2 O2 S2 ] kernel. Compounds 2, 3, and 4 are similar, in all the cases already mentioned the ligand is NH deprotonated and is strongly coordinated to two dimethylthallium(III) units through the N and S atoms. Two additional weak interactions with the O and S atoms lead to a [TlC2 NOS2 ] kernel for the metal atom, in which the coordination polyhedron is a very distorted octahedron with the methyl groups occupying the apical positions. c Central European Science Journals. All rights reserved. Keywords: dimethylthallium(III), 2-mercaptonicotinic acid, esters, complexes, crystal structure

∗

E-mail: [email protected]

Unauthenticated Download Date | 3/25/16 7:13 AM

M. Toma et al. / Central European Journal of Chemistry 2(3) 2004 534–552

1

535

Introduction

Although 2-mercaptonicotinic acid is a ligand with interesting possibilities of coordination, either (N,S) or (O,S), a survey of the reported molecular structure determinations for metal complexes revealed that the S,N-bidentate chelating and N,S-bidentate triconnective bridging modes are the most usual coordination patterns for the 2-mercaptonicotinic acid, (Scheme 1, structures II and IV) [1-4]. The gold(I) complex with the 2-mercaptonicotinic acid describes a S-monodentate coordination mode, (Scheme 1, structure I, [4]). The reported molecular structures of the Mo(VI) complexes with the methyl, ethyl and isopropyl esters reveal that the esters act as N,S-bidentate chelating ligands (Scheme 1, structure IIa) [5].

Scheme 1 Most usual coordination modes of 2-mercaptonicotinic acid and esters.

The presence of the SH- group as substituent in position 2 of the pyridine ring usually leads to a thiol - thione tautomerism which must be considered both in solution and solid state [6].

Scheme 2 Thiol - thione equilibrium for the corresponding ligands.

The present work reports the synthesis and spectral characterization of dimethylthallium(III) complexes with 2-mercaptonicotinic acid (2mna), 2-mercaptomethyl-nicotinate, (2mmn), 2-mercapto-ethyl-nicotinate, (2men) and 2-mercaptoisopropyl-nicotinate, (2min), in 1:1 molar ratio, which permitted the isolation of new dimethylthallium(III) complexes. The compounds were characterized using IR, multinuclear NMR (1 H, 13 C, 205 Tl) and mass spectrometry (electrospray, ES-API). The molecular structures of [TlMe2 (2mna)]·H2 O, (1), [TlMe2 (2mmn)], (2), [TlMe2 (2men)], (3) and [TlMe2 (2min)], (4) were determined by the single-crystal X-ray diffraction. By


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comparison with the reported structures, in 1 the 2-mercaptonicotinic acid acts as a (O;S)-bidentate ligand chelating one dimethylthallium(III) unit and simultaneously bridges (O and S) between two organometallic units.

2

Experimental

2.1 Materials 2-mercaptonicotinic acid was purchased from commercial sources (Fluka). The methyl, ethyl and isopropyl esters were prepared as reported in the literature [7,8] and characterized by 1 H and 13 C NMR. Dimethylthallium(III) iodide was obtained according to the method described by Gilman and Jones [9]. Dimethylthallium(III) hydroxide was prepared by stirring dimethylthallium iodide with an excess of freshly Ag2 O precipitate for 48 hours in water and removing the AgI by filtration. All other chemicals are AR grade and used without additional purification.

2.2 Synthesis An aqueous solution of dimethylthallium hydroxide was added drop wise to a stirred solution of the corresponding ligand (1mmol) in methanol. The final mixture was stirred for 8 hours and then the resultant, a white-yellow precipitate, was recovered via filtration, washed with methanol and dried in vacuum over CaCl2 /KOH. Crystals suitable for single X-ray diffraction studies were obtained by slow evaporation of the solvents from the filtrate of the complexes 1-4. Details of the preparations are given in the Table 1.

a

Starting Me2 TlI g/mmol

materials Ligand g/mmol

Product [yield: g (%)]

M.p. (o C)

Conductivitya (ΛM , Ω−1 cm2 mol−1 )

[TlMe2 (2mna)]·H2 O, 1 [0.267 (64)]

208

49.3

0.372/1.03

2mna 0.160/1.03

[TlMe2 (2mmn)], 2 [0.295 (72)]

182

36.1

0.368/1.02

2mmn 0.173/1.03 2men 0.194/1.06

[TlMe2 (2men)], 3 [0.317 (72)]

198

35.3

0.385/1.06

[TlMe2 (2min)]], 4 [0.315 (68)]

201

33.9

0.390/1.08

2min 0.212/1.08

10−3 M solution in MeOH, ΛM (1:1/MeOH) = 80-115 Ω−1 cm2 mol−1 [10].

Table 1 Preparation data and some physical properties for [TlMe2 (L)] complexes.



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2.3 Measurements Microanalyses, IR, multinuclear NMR spectra, and mass spectra were recorded on crystals for compounds 2 and 3, and on the crude product for the complexes 1 and 4. Elemental analysis (C, H, N, S) was performed using a Fisons 1108 and Perkin Elmer analysers. Melting points were determined with a B¨ uchi apparatus and molar conductivity measurements were made with a Crison CM 2202 apparatus. The analytical data of the complexes are presented in Table 2. IR spectra were recorded on a Br¨ ucker IFS-66 spectrometer using KBr pellets (4000-500 cm−1 ) and Nujol mulls between polyethylene pellets (500-100 cm−1 ). 1 H, 13 C and 205 Tl NMR spectra were recorded on a Br¨ ucker AMX-300 spectrometer operating at 300.14, 75.4 and 173.5 MHz, respectively, using solutions in DMSO-d6 at room temperature. The chemical shifts are reported in ppm and were referenced to TMS using the solvent signal for 1 H and 13 C spectra (1 H: 2.50 ppm, 13 C: 39.50 ppm) and an aqueous TlMe2 NO3 solution after extrapolation to infinite dilution in 205 Tl spectra. Mass spectra were recorded on a Hewlett Packard LC-MSD 1100 apparatus for mass spectrometry using the following experimental conditions: ionization mode: API-ES, polarity: positive, drying gas flow: 10L/min, capillary voltage: 4000 V, mobile phase: 98 % methanol-2 % formic acid. Complex [TlMe2 (2mna)]·H2 O [TlMe2 (2mmn)] [TlMe2 (2men)] [TlMe2 (2min)]

%C

%H

%N

%S

23.69(23.64) 27.18(26.86) 28.69(28.84) 30.64(30.69)

2.94(2.95) 2.96(2.98) 3.32(3.36) 3.69(3.72)

3.51(3.44) 3.50(3.48) 3.39(3.36) 3.21(3.25)

7.69(7.88) 8.04(7.96) 7.41(7.69) 7.54(7.44)

Theoretical values in the brackets.

Table 2 Analytical data for [TlMe2 (L)] complexes.

2.4 Crystallographic data collection and structure determination Data collection and processing was carried out using an Enraf-Nonius CAD 4 diffractometer with a graphite-monochromated Mo-Kα radiation (λ= 0.71073 ˚ A). Cell refinement revealed cell constants corresponding to an orthorhombic cell for 1 (Pbna), 3 (P21 21 21 ) and 4 (P21 21 21 ) and a monoclinic cell for 2 (C2/c), whose dimensions are reported in Tables 3 and 4 along with other experimental parameters. The intensities were corrected using Lorentz polarization factors. The structures were solved using a Patterson method for heavy atoms and refined by full matrix least-squares methods for the location of the remaining non-hydrogen atoms (SHELX 97 [11]). All of the non-hydrogen atoms were treated anisotropically. All hydrogen atoms were included in the model at geometrically calculated positions. The drawings were made using the ORTEP [12] and PLATON [13] programs. Selected distances and bond angles are given in Tables 5 and 6 and the molecules are displayed


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Molecular formula Formula weight Temperature (K) λ(˚ A) Crystal size (mm) Crystal system Space group Unit cell dimension a (˚ A) b (˚ A) c (˚ A) β (o ) V (˚ A3 ) Z Dcalc (g cm−3 ) F000 µ(Mo-Kα) (mm−1 ) θ Range for data collection (o ) Limiting indices (h, k, l) Reflections collected Independent reflections Max. and min. transmissions Refinement method Diffractometer Goodness-of-fit on F 2 Final R indices [I>2σ(I)] Rindices (all data) Largest diff.peak and hole, e˚ A−3 Programs used Deposition number

1

2

C8 H12 NO3 STl 406.62 120(2) 0.71073 0.60 x 0.20 x 0.16 orthorhombic Pbna

C9 H12 NO2 STl 402.63 120(2) 0.71073 0.18 x 0.10 x 0.08 monoclinic C2/c

7.5400(1) 15.9570(3) 18.4190(4)

13.3430(3) 8.2230(2) 21.2220(4) 101.712(1) 2216.10(7) 2279.99(9) 8 8 2.437 2.346 1504 1488 14.746 14.326 2.55–25.00 1.96-25.00 (0, 8); (0, 18); (0, 21) (0, 15); (0, 9); (-25, 24) 3596 3874 1943[R(int) = 0.0150] 2018 [R(int) = 0.0228] 0.2013 and 0.0410 0.3936 and 0.1825 Full-matrix least-squares on F 2 Enraf Nonius CAD 4 1.091 1.065 R1 = 0.023, wR 2 = 0.065 R1 = 0.029, wR 2 = 0.072 R1 = 0.027, wR 2 = 0.068 R1 = 0.033, wR 2 = 0.106 1.420 and –1.663 2.760 and –1.910 SHELX 97 [11], ORTEP [12], PLATON [13] CCDC 235776 CCDC 235777

Table 3 Crystal data and details of the structure refinement for [TlMe2 (2mna)]·H2 O (1) and [TlMe2 (2mmn)] (2).

in the ORTEP diagrams in Figures 1, 3, 4 and 5. Additional material available from the Cambridge Crystallographic Data Center comprises the final atomic coordinates for all atoms, thermal parameters and a complete listing of bond distances and angles.



Molecular formula Formula weight Temperature (K) λ(˚ A) Crystal size (mm) Crystal system Space group Unit cell dimension a (˚ A) b (˚ A) c (˚ A) ˚ V (A3 ) Z Dcalc (g cm−3 ) F000 µ(Mo-Kα) (mm−1 ) θ Range for data collection (o ) Limiting indices (h, k, l) Reflections collected Independent reflections Max. and min. transmissions Refinement method Diffractometer Goodness-of-fit on F 2 Final R indices [F 2 >2σ(F 2 )] Rindices (all data) Largest diff.peak and hole, e˚ A−3 Programs used Deposition number

539

3

4

C10 H14 NO2 STl 416.65 120(2) 0.71073 0.21 x 0.09 x 0.08 orthorhombic P21 21 21

C11 H16 NO2 STl 430.68 293(2) 0.71073 0.02 x 0.03 x 0.16 orthorhombic P21 21 21

8.6860(3) 10.8484(3)) 13.3660(5) 12.5942(7) 4 2.197 776 12.971 2.42–24.99

8.885(2) 11.732(2) 12.996(2) 1354.7(4) 4 2.112 808 12.063 3.13-25.00

(-10, 10); (-12, 12); (-15, 15)

(-8, 9); (-13, 13); (-15, 15)

2195 7410 2195[R(int) = 0.0000] 2251 [R(int) = 0.1138] 0.4234 and 0.1715 0.3936 and 0.1825 Full-matrix least-squares on F 2 Enraf Nonius CAD 4 1.156 0.959 R1 = 0.0214, wR 2 = 0.0503

R1 = 0.0469, wR 2 = 0.0977

R1 = 0.0218, wR 2 = 0.0505

R1 = 0.0836, wR 2 = 0.1084

0.790 and –1.491 1.889 and –2.513 SHELX 97 [11], ORTEP [12], PLATON [13] CCDC 235778 CCDC 235779

Table 4 Crystal data and details of structure refinement for [TlMe2 (2men)] (3) and [TlMe2 (2min)] (4).

3

Results and discussions

3.1 X-ray study The four complexes for which crystal structure determinations are reported in the present work exhibit some common features concerning the metal-ligand bond lengths: ˚ (i) the structural parameters of the TlMe+ 2 unit [Tl-C = 2.123(6)-2.162(14) A, C-Tl-C = 158.0(6)-174.3(2)o ] are similar to the reported values for other Me2 Tl+ complexes with (N, S), or (O, S)-donor ligands [Tl-C = 1.97(4)-2.199(8) ˚ A, C-Tl- C = 106(1)-180o [14]].


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(ii) the Tl-N distances are in the range [2.574(10)-2.615(5) ˚ A]. These values are greater ˚ than those found in [TlMe2 (2-SPy)] (2.494(7) A, [15]), but are similar with those ˚ [16]), [TlMe2 (Py)2 CH2 ](NO3 ) found in complexes [TlMe2 (phen)](ClO4 ) (2.57(27) A, ˚ [17]), [TlMe2 (terpy)(H2 O)](NO3 ) (2.620(10), 2.650(9) and (2.658(9), 2.666(9) A, ˚ [18]). (rvdW = 3.55 2.631(10) ˚ A, [17]), [TlMe2 T(pic)] (2.586(10) and 2.567(11) A, ˚ A, [19]). (iii) Tl-S bond distances [2.7765(13)-3.0874(12) ˚ A] compared with the Tl-S bond lengths observed in dimethylthallium(III) complexes with 2-mercapto-pyridine (2.870(2) ˚ A, ˚ ˚ [15]), 1-hydroxy-2-pyridine-thione (2.889(2) A, [20]) and thiouracil (2.869(8) A, [21]) are consistent with medium-weak metal-sulfur bonds. However, some longer Tl-S distances: [3.2198(11)-3.341(14) ˚ A] suggest weaker coordinative thallium-sulfur ˚ interactions. ( rvdW = 3.55 A, [19]) ˚ are similar with (iv) the Tl-O distances in 1 (Tl-O(1) = 2.522(3), Tl-O(1’) = 2.589(3) A) those found in dimethylthallium complexes with picolinic acid (2.532(9) and 2.501(9) ˚ ˚ [18]), corresponding A, [18]) and 3-hydroxy-picolinic acid (2.502(4) and 2.555(4) A, to the same coordination pattern of the carboxylate group. The bond lengths ˚ [22]) are shorter than those observed in [TlMe2 (H2 Tot)(H2 O)] (2.668(9), 2.86(1) A, and [TlMe2 (propynoic acid)] (2.65(2) and 2.76(2) ˚ A, [23]). The Tl-O(2’) distance ˚ [3.403(3) A], is shorter than the sum of the van der Waals radii Tl-O = 3.50 ˚ A [19] and is consistent with a very weak metal-oxygen interaction which can not be considered a proper bond length as, i.e.Tl-O(1) = 2.522(3), or Tl-O(1’) = 2.589(3) ˚ A). This value is similar with that found in the crystal structure of [TlMe2 (3hpic)] ˚ [18]]. The Tl-O bond lengths with the oxygen atom belonging to [3.462(5) A, the COOR group (2.974(4), 2.895(4), 2.875(10) ˚ A) are similar with those found ˚ [18]), in [TlMe2 (terpy)(H2 O)](NO3 ) (2.932(12), [17]), [TlMe2 (3hpic)] (2.966(4) A, [TlMe2 (2anic)] (2.864(4) ˚ A, [23]). ˚ in 2, 3 and 4] are shorter (v) the C-S distances [1.714(4) in 1 and 1.728(15)-1.747(6) A than the distance of a simple C-S bond (1.79 ˚ A), but longer than the distance ˚ of a double C=S bond (1.69 A) [25].These values suggest that the ester ligands significantly evolve, after deprotonation and coordination, to the thiol form, while this evolution is less significant for the 2-mercaptonicotinic acid. (vi) the C-O distances of the coordinated carboxylate group of 2-mercaptonicotinic acid in 1 [1.269(5) and 1.251(5) ˚ A] are shorter than the distance of a simple C-O bond ˚ (1.50 A [25]) but longer than the distance of a double C=O bond (1.21 ˚ A [25]); as a result of the redistribution of the electronic charge in the deprotonated and strongly coordinated carboxylate group. The magnitude of the carbon-oxygen bonds from the COOR groups in the complexes 2-4 is consistent with C=O double bonds ˚ vs. 1.210(3)-1.229(8) ˚ [1.184(18)-1.209(7) A A [18] in the free esters] and C-O single ˚ ˚ [18] in the free esters]. bonds [1.329(8)-1.353(17) A vs. 1.339(2)-1.351(8) A



1

541

2

Tl-C(8) Tl-C(7) Tl-O(1) Tl-O(1)’ Tl-O(2)’ Tl-S Tl-S”

2.123(6) 2.125(5) 2.522(3) 2.589(3) 3.403(3) 3.0874(12)) 3.2198(11)

Tl-C(8) Tl-C(9) Tl-N Tl-S Tl-S’ Tl-O(1)’

2.128(6) 2.123(6) 2.615(6) 3.3357(17) 2.7822(14) 2.974(4)

C(6)-O(1) C(6)-O(2) C(5)-S

1.269(5) 1.251(5) 1.714(4)

C(6)-O(1) C(6)-O(2) C(7)-O(2) C(1)-S

1.207(8) 1.329(8) 1.443(8) 1.747(6)

C(8)-Tl-C(7) C(7)-Tl-O(1) C(7)-Tl-O(1)’ C(7)-Tl-S C(7)-Tl-S” C(7)-Tl-O(2)” C(8)-Tl-O(1) C(8)-Tl-O(1)’ C(8)-Tl-S C(8)-Tl-S” C(8)-Tl-O(2)’ O(1)-Tl-O(1)’ O(1)-Tl-S O(1)-Tl-S” O(1)-Tl-O(2)’ O(1)’-Tl-S O(1)’-Tl-S” O(1)’-Tl-O(2)’ S-Tl-S” S-Tl-O(2)’ S”-Tl-O(2)’

174.3(2) 93.76(16) 87.10(14) 93.89(14) 79.26(15) 74.33(14) 91.03(14) 91.60(13) 90.74(12) 96.47(12) 101.10(13) 69.72(12) 69.55(7) 169.01(7) 109.14(9) 139.24(7) 117.90(7) 40.82(8) 102.21(3) 168.14(5) 77.34(5)

C(8)-Tl-C(9) C(8)-Tl-O(1)’ C(8)-Tl-S’ C(8)-Tl-N C(8)-Tl-S C(9)-Tl-O(1)’ C(9)-Tl-S’ C(9)-Tl-S C(9)-Tl-N O(1)’-Tl-S’ O(1)’-Tl-S O(1)’-Tl-N S-Tl-S’ N-Tl-S’ N-Tl-S

160.8(3) 87.0(2) 97.35(17) 101.0(2) 77.34(17) 84.5(2) 95.93(18) 103.96(19) 94.3(2) 70.44(10) 154.52(10) 153.22(15) 130.92(3) 83.13(11) 51.42(12)

1: ’ = x, -y+1/2, -z+1; ” = -x+1, -y, -z+1, 2: ‘ = -x+1/2, y-1/2, -z+3/2.

Table 5 Selected bond lengths (˚ A) and angles (deg.) for compounds 1 and 2.

3.2 Crystal structure of [TlMe2 (2mna)]·H2 O (1) The X-ray crystal structure of 1 is shown in Figure 1. The deprotonated carboxylate group of the 2mna ligand coordinates two [TlMe2 ]+ units as a monodentate bridge through Unauthenticated Download Date | 3/25/16 7:13 AM

542


3

4


2.138(6) 2.148(5) 2.589(4) 3.2884(15) 2.7765(13) 2.895(4)


2.133(14) 2.162(14) 2.574(10) 3.341(4) 2.780(4) 2.875(10)

C(6)-O(1) C(6)-O(2) C(7)-O(2) C(1)-S

1.209(7) 1.332(7) 1.458(7) 1.745(5)

C(6)-O(1) C(6)-O(2) C(9)-O(2) C(5)-S

1.184(18) 1.353(17) 1.482(17) 1.728(15)

C(9)-Tl-C(10) C(9)-Tl-N C(9)-Tl-S C(9)-Tl-S’ C(9)-Tl-O(1)’ C(10)-Tl-N C(10)-Tl-S C(10)-Tl-S’ C(10)-Tl-O(1)’ N-Tl-S N-Tl-S’ N-Tl-O(1)’ O(1)’-Tl-S S’-Tl-S S’-Tl-O(1)’

158.1(3) 89.7(2) 95.71(18) 99.38(19) 88.20(19) 106.50(18) 83.79(19) 97.72(18) 85.55(18) 51.29(10) 80.58(10) 148.02(13) 160.55(9) 129.29(3) 68.32(9)

C(7)-Tl-C(8) C(7)-Tl-N C(7)-Tl-S C(7)-Tl-S’ C(7)-Tl-O(1)’ C(8)-Tl-N C(8)-Tl-S C(8)-Tl-S’ C(8)-Tl-O(1)’ N-Tl-S N-Tl-S’ N-Tl-O(1)’ S-Tl-O(1’) S’-Tl-S S’-Tl-O(1)’

158.0(69 105.4(5) 82.9(4) 99.1(5) 85.7(5) 90.0(5) 95.2(4) 98.6(4) 88.2(4) 51.2(3) 82.1(3) 150.9(3) 157.8(2) 131.18(7) 69.5(2)

3: ’ = x+1/2, -y+1/2, -z+1; 4: ’ = x+1/2, -y+3/2, -z.

Table 6 Selected bond lengths (˚ A) and angles (deg.) for compounds 3 and 4.

O(1) forming strongly bonded dimmers. The NH group remains protonated, thus the N atom does not coordinate and the ligand basically keeps the thione form. Nevertheless, although in the thione form, the S atom is weakly bonded to two metal atoms from neighboring dimmers giving rise to a polymeric chain (see Fig 1b) along the y axis. The resulting [TlC2 O2 S2 ] kernel is a distorted octahedron with the methyl groups occupying the apical position. The equatorial positions are occupied by two oxygen atoms and two sulfur atoms [ eq = 359.4o ]. The distortion of the coordination polyhedron is mainly due to the O-Tl-S angles [O(1)-Tl-S 69.55(7), O(1’)-Tl-S” 117.90(7)o ] and O(1’)-Tl-O(1) 69.72(12)o .



543

(a)

(b) Fig. 1 ORTEP plots of 1 showing (a) the numbering scheme in the asymmetric unit and the dimmer association and (b) fragment of the polymeric chain.

In the lattice, chains of 1 are linked through hydrogen bonds involving the NH group, the oxygen O(2) of the carboxylate group and the water molecule (table 7, Figure 2), give rise to an infinite three-dimensional network (see Table 7, Fig. 2).


544


D-H· · ·A N-H· · ·O(1w)iii O(1w)-H(11w) ··O(2)iv O(1w)-H(12w) ··O(2) iii iv

D-H

H......A

D....A

DHA

0.8800 0.6594 0.9292

1.8537 2.1518 1.8485

2.7197 2.8065 2.7259

167.57 171.37 156.48

= 1.5-x, -0.5+y, 0.5+z, = 0.5+x, y, 0.5-z.

Table 7 Hydrogen bonding (˚ A, deg) in [TlMe2 (2mna)]·H2 O.

Fig. 2 PLATON diagram of the hydrogen bonds in [TlMe2 (2mna)]·H2 O.

3.3 Crystal structure of [TlMe2 (2mmn)](2), [TlMe2 (2men)](3) and [TlMe2 (2min)] (4) In these complexes the three mercaptonicotinato ligands show a very similar coordinative behavior. In fact, in the three complexes each ligand bridges between two dimethylthallium(III) units, being strongly bonded to one of these units via the pyridinic N atom (N-Tl), and to the other via the S atom [S-Tl”, ” = -x+0.5, y+0.5, -z+1.5 (2), x-0.5, -y+0.5, -z+1 (3), x-0.5, -y+1.5, -z (4)], giving rise to a polymeric chains (see Figure 3 for compound 2, similar chains are obtained for 3 and 4) along the y (for 2) and the x axes (for 3 and 4). Furthermore, each ligand also establishes two weak interactions, with two different metal atoms, through sulfur (S· · ·Tl) and oxygen O1 (O1· · ·Tl”) atoms. If all



545

these strong and weak interactions are taken into account the coordination number of the thallium is six with a [TlC2 NOS2 ] kernel, and the coordination polyhedron around the metal is described as a very distorted octahedron with the methyl groups in the apical positions. The C-Tl-C units form similar angles which are far from linearity and bent towards the vacant position. The equatorial positions are occupied by two sulfur atoms, a nitrogen atom and an oxygen atom, [ eq = 359.5-360.7o ].

Fig. 3 ORTEP plot showing the numbering scheme and the supramolecular association in [TlMe2 (2mmn)] (2).

Fig. 4 ORTEP plot of the asymmetric unit in [TlMe2 (2men)](3).

Fig. 5 ORTEP plot of the asymmetric unit in [TlMe2 (2min)](4).


546


3.4 IR spectra The main infrared (1800-100 cm−1 ) frequencies of the free ligands and complexes are listed in Table 8 and 9. Compound

ν(C=O)

ν(CN), δ(NH), νPy

ν(C=S)

ν(C–S)

2mna 1 2mmn 2 2men 3 2min 4

1681s 1691vw 1726s 1711vs 1731s 1709s 1727s 1707s

1598w, 1566m, 1500m, 1445w 1572s, 1501vw, 1439vw 1602ms, 1561s, 1502sh, 1476m 1604vw, 1570m, 1546m, 1442m 1602ms, 1569m, 1549sh, 1447w 1636w, 1553m, 1501sh, 1441w 1606m, 1584m, 1498m, 1441m 1606w, 1573m, 1550m, 1452w

1142w 1154m 1140m 1122m 1145m 1130ms 1149ms 1138ms

639w 634w 641s 657w 643s 658w 642m 659vw

s = strong, vs = very strong, m = medium, ms = medium-strong, w = weak, vw = very weak, sh = shoulder

Table 8 Significant IR absorption bands (1800-1000 cm−1 ) of the free ligands and complexes.

Complex

ν(Tl-C)

ν(Tl-O)

ν(Tl-S)

ν(Tl-N)

1 2 3 4

552w, 475m 535w, 487m 554w, 448w 530w

370m, 316m -

245m 262vw 244m 260w

200w 200m 221w

m = medium, w = weak, vw = very weak

Table 9 Main far IR data (600-100 cm−1 ) for the [TlMe2 (L)] complexes.

The C=O stretching vibration band is shifted to higher frequencies (∆ν = 10 cm−1 ) in the IR spectrum of the complex 1 by comparison with the spectrum of the free acid. The difference ∆ν = ν(COO)asym − ν(COO)symm which can be correlated with the coordination pattern of the carboxylate group [26] could not be determined accurately in the spectrum of 1 due to the overlap of the ν(COO)asym with the stretching vibration of the C=N bond (ν(COO)symm = 1397 cm−1 ). These IR results are in concordance with a monodentate coordination mode for the carboxylate group of the 2-mercaptonicotinic acid. The ν(C=O) band is shifted in the spectra of the complexes 2-4 to lower wave numbers (∆ν = 15-22 cm−1 ). The absorption bands in the 1636-1441cm−1 range in the spectra of the complexes 1-4 are corresponding to strongly mixed [ν(C=N), δ(CN), δ(NH) and ν(Py)] modes. The assignment of the ν(C-S) and ν(C=S) stretching modes in the spectra of complexes 1-4 by comparison with the IR spectra of the free ligands was made on the basis of the published data for [M3 (MENA)3 Cl3 ], M = Pd,Pt [1], [TlMe2 (2-Spy)] [15] and [TlMe2 H2 Tot·H2 O] [22]. In the spectrum of the complex 1 the ν(C=S) shifts to higher frequencies (∆ν = 12 cm−1 ). The absorption band characteristic to ν(C-S)



547

stretching vibration has almost the same position and intensity in the spectrum of the complex 1 (634 cm−1 ) as in the spectrum of the free ligand (639 cm−1 ). These results suggest a coordination of the acid in the thione form, which is in good agreement with the crystallographic study. The shift of the ν(C=S) band to lower wave numbers (∆ν = 11-18 cm−1 ) and of the ν(C-S) mode to higher frequencies (∆ν = 15-17 cm−1 ) in the spectra of the complexes 2-4 is in concordance with the coordination of the esters in the thiol form. Stretching vibrations are assigned for Tl-C, Tl-O, Tl-S and Tl-N bonds in the far IR (600-100 cm−1 ) spectra of all four complexes and are within the range for dimethylthallium(III) complexes with (O,S) and (N,S) donor-ligands [15, 16, 18, 20-22, 27].

3.5 NMR spectra The NMR spectra were recorded in DMSO-d6 and the assignment of the 1 H and 13 C resonance signals are included in Tables 10 and 11. The numbering pattern is shown in Scheme 3.

Scheme 3 Numbering scheme used for studied systems.

The main changes in the 1 H NMR spectra of the complexes with respect to the free ligands are: • The presence of the resonance signal of the TlMe+ 2 unit as a broad doublet in 2 the 0.87–0.86 ppm range ( JT l−H = 412.80–416.91 Hz). These spectral parameters 2 are within the normal range for the TlMe+ 2 complexes (0.68-1.49 ppm, JT l−H = 349-441.5Hz [15, 20, 21, 22]). • The absence of signals about 14-13 ppm in the spectrum of the complex [TlMe2 (2mna)], together with the fact that water signal is very wide, is coherent with the monodeprotonation of the ligand and the remaining proton exchanging with the solvent. • The resonance signal in 13.72–13.78 ppm range is due to the NH group considering that in DMSO-d6 solution the esters are in the thione form. The absence of this signal in the spectra of the complexes is a result of the deprotonation and coordination through the pyridyl nitrogen atom. • The resonance signal of H(6) is shifted upfield (0.31 ppm) in the spectrum of the complex 1 because the pyridyl nitrogen atom does not coordinate itself and downfield


548


Compound

NH

H(6)

H(4)

H(5)

CH3

CH2

CH

TlMe+ 2

2mna 1 2mmn 2 2men 3 2min 4

14.55s* 13.76s 13.72s 13.78s -

8.50dd 8.19dd 7.75t 8.11dd 7.74t 8.11dd 7.73t 8.11dd

8.14dd 8.08dd 7.66dd 7.59dd 7.64dd 7.58dd 7.60dd 7.55dd

7.12dd 6.91dd 6.78t 6.81dd 6.77t 6.81dd 6.77t 6.81dd

3.75s 3.73s 1.25t 1.26t 1.25t 1.28d

4.22q 4.20q -

5.05m 5.04m

0.87d 0.86d 0.86d 0.86d

* This signal also includes the COOH proton, s = singlet, d = doublet, dd = doublet of doublets, t = triplet, q = quadruplet, m = multiplet. H(6): 3 JHH = 5.02 Hz (1), 4.98 Hz (2), 4.98 Hz (3), 5.01 Hz (4); 4 JHH = 1.80 Hz (1), 1.72 Hz (2), 1.72 Hz (3), 1.89 Hz (4) H(4): 3 JHH = 7.62 Hz (1), 7.50 Hz (2), 7.49 Hz (3), 7.49 Hz (4); 4 JHH = 1.68 Hz (1), 1.71 Hz (2), 1.72 Hz (3), 1.92 Hz (4) H(5): 3 JHH = 5.09 Hz (1), 5.03 Hz (2), 5.10 Hz (3), 5.12 Hz (4); 3 JHH = 7.62 Hz (1), 7.50 Hz (2), 7.49 Hz (3), 7.49 Hz (4) 2J

T l−H

= 416.91 Hz (1), 414.09 Hz (2), 413.73 Hz (3), 412.80 Hz (4)

Table 10 1 H NMR data (δ, ppm) for the free ligands and [TlMe2 (L)] complexes.

(0.35–0.38 ppm) in the spectra of the complexes 2-4 as a result of a N-coordination mode. • The signals of the H(4) and H(5) protons are shifted upfield in the spectra of the complexes 1-4 as a result of coordination of the ligands. • The resonance signals of the alkyl protons (methyl, ethyl and isopropyl) have almost the same positions as in the free ligands. The 13 C NMR spectra of the complexes (spectral data in the Table 11) present the following changes: • The spectra of the complexes present the carbon resonance signals of the TlMe+ 2 unit 1 13 in the 24.40–21.41 ppm range ( JT l−C = 2995.87–3017.32 Hz). These C spectral parameters are within the normal range for the TlMe+ 2 complexes (19.7–28.7 ppm, 1 JT l−C = 2267.7–3032.2 Hz, [15, 21, 22, 27]. • The C(7) resonance signal is shifted downfield (3.18–0.99 ppm) in the spectra of the complexes 1-4. The greater difference with respect to the spectrum of the free ligand is observed in the spectrum of the complex 1 (3.18 ppm) as a result of a strong coordination through the carboxylate group. • In the spectra of the complexes the C(6) signal is shifted downfield (3.82, 7.74-8.70 ppm). The lowest difference appears in the spectrum of the complex 1 because, in this case, the pyridyl nitrogen atom does not coordinate. • C(2) signal has almost the same positions in the spectrum of the complex 1 because, in this case, on the one side the nitrogen atom does not coordinate and on the other side the ligand coordinates in the thione form as the free ligand. In the spectra of the complexes 2-4 this signal is shifted upfield (0.63-1.48 ppm) as a result of the



549

(N,S) coordination mode. • The C(3) and C(4)resonance signals are shifted upfield (0.20-5.50/0.52-4.27 ppm) in the spectra of complexes, while the C(5) signal is shifted downfield (0.45, 2.44-3.40 ppm) in the spectra of the complexes. Compound

C(7)

C(6)

C(2)

C(4)

C(3)

C(5)

CH3

CH2

CH

TlMe+ 2

2mna

165.20

143.91

173.20

143.22

129.50

115.04

-

-

-

-

1

168.38

147.73

173.03

138.95

129.30

115.49

-

-

-

24.40

2mmn

166.71

140.00

174.57

136.95

136.49

111.94

.52.18

-

-

-

2

167.74

147.74

173.15

135.77

130.99

114.38

51.68

-

-

21.43

2men

166.19

139.87

174.57

136.70

135.69

111.89

13.89

60.89

-

-

3

167.18

147.64

173.09

135.64

131.15

114.39

14.05

60.27

-

21.44

2min

164.79

138.83

173.61

135.98

135.48

110.98

20.52

-

67.52

-

4

166.70

147.53

172.98

135.46

131.44

114.38

21.58

-

67.64

21.41

(*) 1 JT l−C = 2995.87 Hz (1), 3013.03 Hz (2), 3017.32 Hz (3), 3012.40 Hz (4).

Table 11

13

C NMR data (δ, ppm) for the free ligands and [Me2 Tl(L)] complexes.

The 205 Tl spectra of the complexes with the esters are characterized by a broad signal situated at 3684, 3690 and 3695 ppm, respectively, which is specifically for a (N,S) coordination mode of the TlMe+ 2 [15, 21, 22, 27]. The spectrum of the complex [TlMe2 (2mna)] has a broad signal at 3498 ppm characteristic to a (O,S) coordination. [18].

3.6 Mass spectra The results of the ES-API mass spectra of the complexes are listed in Table 12. In the ES mass spectra recorded at low cone voltage (25 V) the peaks with m/z = 390, 404, 418 and 432 are corresponding to the ion [M+ H+ ], in good agreement with the proposed molecular formula. The other peaks correspond to the ions formed after the loss of a methyl group form the TlMe+ 2 unit or of R-, RO-, -COOR groups [20, 27, 28, 29].

4

Supplementary material

Crystallographic data for the structural analysis of the compounds 1-4 have been deposited with the Cambridge Crystallographic Data Center. Copies of the information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44–1223–336033, e-mail: [email protected], or www: http://www.ccdc.cam.ac.uk.


550


Complex

m/z

[M],[M+H+ ],[M-R]

Relative abundance

[TlMe2 (2mna)]·H2 O M = 389/407*

624 390 235 638 571 404 235 652 418 235 666 432 235

[M+TlMe+ 2] + [M+H ] [TlMe+ 2] [M+TlMe+ 2] [M+L] [M+H+ ] [TlMe+ 2] [M+TlMe+ 2] + [M+H ] [TlMe+ 2] [M+TlMe+ 2] + [M+H ] [TlMe+ 2]

25 37 100 100 8 26 25 100 6 20 80 100 15

[TlMe2 (2mmn)] M = 403

[TlMe2 (2men)] M = 417 [TlMe2 (2min)] M = 431

(*) Nominal values are calculated for the most abundant isotope

205 Tl.

Table 12 ES-mass spectral data for the complexes [TlMe2 (L)] recorded at cone voltage of 25V.

Acknowledgment M.T. gratefully acknowledges the Agencia Espa˜ nola de Cooperación Internacional (fellowship) and the Department of Inorganic Chemistry, University of Santiago de Compostela, Spain.

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