Sep 18, 1995 - SERGIO A. MOYA. Departamento de Quimica, Facultad de .... (a) D. J. Cole Hamilton, J. Chem. Soc., Chem. Commun. 1980, 1213; (b) D.
Polyhedron Vol. 15, No. 9, pp. 1571 1573, 1996
~
Pergamon 0277-5387(95)00469-6
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COMMUNICATION SOLUBLE RUTHENIUM CARBONYL COMPLEXES CONTAINING NEW STERICALLY HINDERED BIPYRIDINE LIGANDS TAIBI BEN HADDA and ISMAIL ZIDANE D6partement de chimie, Universit6 Mohammed ler, Facult6 des Sciences, Oujda, Morocco
and SERGIO A. MOYA Departamento de Quimica, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 307-2, Chile
and HUBERT LE BOZECt Laboratoire de Chimie de Coordination Organique (URA CNRS 415), Campus de Beaulieu, Universit6 de Rennes 1, 35042 Rennes Cedex, France
(Received 18 September 1995; accepted 27 September 1995) Abstract--The synthesis, characterization and reactivity of bipyridyl ruthenium carbonyl complexes of the type Ru(NN)(CO)2C12 [where NN = 4,4'-tBu2-2,2'-bpy (bpy*, a) ; 6,6'Me2-4,4'-tBu2-2,2'-bpy (dmbpy*, b); 6,6'-Ph:-4,4'-tBu2-2,2'-bpy (dpbpy*, c)] is reported together with the synthesis and characterization of Ru(dpphen)(CO)2C12 [where dpphen = 2,9-Ph2-1,10-phen, d]. When NN is bpy* or dmbpy*, the cis-carbonyl, transchloro isomer is obtained, whereas when NN is dpbpy* or dpphen the cis-carbonyl, cischloro isomer is the predominant product.
The synthesis and catalytic properties of polypyridine complexes of ruthenium have been extensively studied over a period of years, particularly those containing the ligand 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen). For example bipyridyl ruthenium carbonyl complexes have proved to be active catalysts in the water-gas shift reaction 1 and in the electrochemical 2 and photochemicaP reduction of CO2 to CO and formate. On the other hand, several ruthenium complexes containing sterically hindered bpy or phen ligands have been implicated in other catalytic processes such as the
t Author to whom correspondence should be addressed.
oxidation of organic substrates 4 and the hydrogenation of ketones and olefines. 5 In previous papers we have shown that 2,2'bipyridine and 2,2',2"-terpyridine containing tertbutyl substituents greatly enhance the solubility of the resultant complexes in common organic solvents. 6 Pursuing our interest in the chemistry of soluble bipyridine ruthenium complexes we sought to design new sterically hindering ligands derived from 4,4'-di-tert-butyl-2,2'-bipyridine (bpy*). In this communication we report the synthesis of ruthenium carbonyl complexes containing bpy*, two new 6,6'-disubstituted 2,2'-bipyridine derivatives b-c and the 2,9-diphenyl-l,10 phenanthroline ligand (dpphen) 7 (Scheme 1). 6,6' - Dimethyl- 4,4' - di - tert- butyl - 2,2' - bipyridine
1571
Communication
1572
d : dpphen
a : bpy* (R = H) b : dmbpy* (R = Me) c : dpbpy* (R = Ph) Scheme 1.
(dmbpy*, b) and 6,6'-diphenyl-4,4'-di-tert-butyl2,2'-bipyridine (dpbpy*, c) were prepared in high yield (85-95%) by reacting bpy* with methyl lithium and phenyl lithium, respectively, followed by hydrolysis and oxidation with manganese dioxide. 8 The pale yellow complexes Ru(bpy*)(CO)aC12(la) and Ru (dmbpy*)(CO)2C12 (lb) were typically prepared in good yield by reacting bpy* and dmbpy* with the "red carbonyl solution" in refluxing 3/1/1 ethanol/water/acetonitrile solution 9 [eq. (1)]. Both compounds showed two strong v(CO) vibrations at ca 2050-2000 cm -~ in the IR spectra and the IH N M R spectra displayed only one signal for the tertbutyl groups.t These data clearly indicate a ciscarbonyl, trans-chloro structure for complexes la and lb.
With the more hindered dpbpy* ligand c the same procedure allowed the formation of a mixture containing several products. Chromatographic purification (alumina) led to isolation of the beige compound Ru(dpbpy*) (CO)2C12 in 37 % yield, having the cis-carbonyl, cis-chloro structure l'e [eq. (2)]. This stereochemical assignment was established by IR andlH N M R spectroscopy.t The IR spectrum showed two strong v(CO) bands (2027 and 1960 c m - l ) at lower frequencies than those of l a b , but similar to those already observed by Kelly et al. for the cis-carbonyl, cis-chloro isomer of Ru (bpy)(CO)2Cl2 .ga The ~H N M R spectrum showed two signals for the tert-butyl protons, characteristic of a dissymmetric bipyridine ligand. This complex was more readily prepared in 69% yield by reacting stoichiometric amounts of RuC13"3H20 and dpbpy* e in refluxing D M F for 10 h [eq. (2)]. The IR spectrum of the crude product before chromatographic purification exhibited, in addition to the two strong v(CO) frequencies of l'e, two very weak v(CO) bands at 2056 and 1994 cm -~ which could be attributed to the cis-carbonyl, trans-chloro isomer lc. New complexes la, lb and l'e are soluble in weak polar solvents such as dichloromethane, T H F and toluene, and even slightly soluble in ether.
C1 EtOH/H20/CH3CN [Ru(CO)2C12] n
+ N
N
~ N,,,.
,,,CO
A
(1) C1 l a (bpy*) lb (dmbpy*)
[Ru(CO)2C12]n t~.~
/
EtOH/H20'A "
N N
~
C1 f , N , , . . ~ ........CO
(Ni DMF,
A
i .C,
(2)
l'e (dpbpy*) l'd (dpphen)
f Selected IR and NMR data: la: IR (KBr) v/cm 1 2056 (vs), 2001 (vs), 1610 (s), 1410 (s) ; IH NMR (300 MHz, CD2C12, 297 K) &9.01 (d, 2H, J = 5.9 Hz) ; 8.18 (d, 2H, J = 1.9 Hz) ; 7.64 (d, 2H, J = 5.9 and 1.9 Hz) ; 1.43 (s, 18H, But). lb: IR (KBr) v/cm -j 2055 (vs), 1988 (vs), 1613 (s), 1447 (s); 1H NMR (300 MHz, CDC13, 297 K) 6 8.16 (d, 2H, J = 1.2 Hz); 7.07 (d, 2H, J = 1.2 Hz); 2.55 (s, Me); 1.29 (s, But). l'c: IR (KBr) v/cm J 2077 (vs), 1960 (vs), 1611 (s), 1543 (s), 1390 (s); ~H NMR (300 MHz, CDCI3, 297 K) 6 8.03 (d, 1H, J = 1.7 Hz); 7.85 (s, IH); 7.81 (s, 1H) ; 7.72 (d, 1H, J = 7.6 Hz) ; 7.66-7.54 (m, 8H) ; 7.07 (m, 2H) ; 1.48 (s, 9H, But) 1.44 (s, 9H, But) ; 2 : IR (KBr) v/cm -~ 1988 (vs), 1617 (s), 1436 (s) ; IH NMR (300 MHz, CDzC12, 297 K) 6 9.08 (dd, 1H, J = 6.0 and 2.8 Hz) ; 8.36.4 (m, H arom dppe and bpy*) ; 3.13 (m, 2H, CH2P) ; 2.85 (m, 2H, CH2P) ; 1.45 (s, 9H, But) ; 1.23 (s, 9H, But) ; 31p NMR (121.5 MHz, CDC13, 297 K) 6 61.54 (d, J = 12.3 Hz) ; 49.73 (d, J = 12.3 Hz) ; 13C NMR (75.5 MHz, CDC13, 297 K) &201.3 (dd, CO, JPc = 17.4 and 13.2 Hz).
Communication The two procedures were used to prepare Ru(dpphen)(CO)2C12 [eq. (2)]. This compound was obtained in 72-75% yield as the sparingly soluble cis-carbonyl, cis-chloro isomer l'd. Again two weak v(CO) bands (2057 and 1994 cm -~) due to the ciscarbonyl, trans-chloro isomer ld was observed beside the two strong absorption bands (2029 and 1959 cm-~) of the major isomer I'd [l'd/ld ~ 95/5] in the IR spectrum of the crude precipitate. The reactivity of l a was further examined. This compound was found to react with the diphosphine ligand dppe, either thermally in refluxing aqueous ethanol or photochemically in dichloromethane, to form the new mixed diphos-bipyridine complex 2 in 82-92% yieldt [eq. (3)].
1573 REFERENCES
1. (a) D. J. Cole Hamilton, J. Chem. Soc., Chem. Commun. 1980, 1213; (b) D. Choudhury and D. J. Cole Hamilton, J. Chem. Soc., Dalton Trans. 1982, 1985; (c) K. Tanaka, M. Morimoto and T. Tanaka, Chem. Lett. 1983, 901 ; (d) M. Ishida, K. Tanaka, M. Morimoto and T. Tanaka, Organometallies 1986, 5, 724 ; (e) J. G. Haasnoot, W. Hinrichs, O. Weir and J. G. Vos, Inorg. Chem. 1986, 25, 1440. 2. (a) M. Ishida, K. Fujicki, T. Omba, K. Ohkubo, K. Tanaka, T. Terada and K. Tanaka, J. Chem. Soc., Dalton Trans. 1990, 2155; (b) M. Ishida, K. Tanaka and T. Tanaka, Organometallics 1987, 6, 181 ; (c) M. N. Collomb-Dunand-Sauthier, A. Deronzier and R. Ziessel, Inorg. Chem. 1994, 33, 2961.
C1 N, ] ,,,CO "°"Ru .o*
(3) 1"1 " co
C1 A, EtOH/H20 (82%) + dppe
r
or by, CH2CI2 (92%)
+
N,,,..du ... "CO
fl
(3)
C1 la
In conclusion of this preliminary work, we have developed the synthesis of new soluble bipyridyl ruthenium carbonyl complexes and we have shown that the presence of sterically hindering phenyl substituents ~ to the nitrogen atoms favors the formation of the cis-chloro, cis-carbonyl isomers. Works are in progress to evaluate the catalytic properties of these complexes.
Acknowledgements--We thank the CNRS, the FON-
DECYT and the ECOS project (France-Chile) for financial support. The University of Oujda (Morocco) is gratefully acknowledged for providing a leave of absence for T.B-H.
2
3. (a) J. M. Lehn and R. Ziessel, J. Organomet. Chem. 1990, 382, 157; (b) M. Ishida, T. Terada, K. Tanaka and T. Tanaka, Inor9. Chem. 1990, 29, 905 ; (c) J. R. Pugh, M. R. M. Bruce, B. P. Sullivan and T. J. Meyer, Inor9. Chem. 1991, 30, 86. 4. (a) C-M. Che and W-H. Leung, J. Chem. Soc., Chem. Commun. 1987, 1376; (b) A. S. Goldstein and R. S. Drago, J. Chem. Soc., Chem. Commun. 1991, 21. 5. C.-P. Lau and L. Cheng, J. Mol. Catal. 1993, 84, 39. 6. (a) T. Ben Hadda and H. Le Bozec, Inor#. Chim. Acta 1993, 204, 103 ; (b) T. Ben Hadda, C. Mountassir and H. Le Bozec, Polyhedron 1995, 14, 953. 7. C.O. Dietrich-Bucheker, P. A. Marnot and J. P. Sauvage, Tetrahedron. Lett. 1982, 23, 5291. 8. T. Ben Hadda, Thesis, University of Oujda (1995). 9. (a) J. M. Kelly, C. M. O'Connell and J. G. Vos, lnorg. Chim. Acta 1982, 64, L75; (b) M. N. CollombDunand-Sauthier, A. Deronzier and R. Ziessel, J. Electroanal. Chem. 1991, 319, 347.
