Synthesis, properties and molecular structure of [Ru(tpm)(bpy)(CH3CN)](PF6)2 (tpm = tris(1-pyrazolyl)methane, bpy = 2,2?-bipyridine). Another example of nitrile hydrolysis catalysed by ruthenium(II),

KATZ, NÉSTOR E.; FAGALDE, FLORENCIA; LIS DE KATZ, NOEMÍ D.; MELLACE, MARÍA G.; ROMERO, ISABEL; LLOBET, ANTONI; BENET-BUCHHOLZ, JORDI

Mérida, México

Congreso; XXXVI International Conference on Coordination Chemistry; 2004

ICC

The new complex [Ru(tpm)(bpy)(CH3CN)](PF6)2 (with tpm= tris(1-pyrazolyl)methane, bpy= 2,2?-bipyridine) has been prepared. Its IR spectrum points to a strongly diminished p-backbonding from Ru(II) to the nitrile group, caused by competition with bpy. The absorptions visible bands can be assigned to Ru(II) ® bpy MLCT transitions, with maximum wavelength values being consistent with the obtained electrochemical and photophysical data in CH3CN . A ruthenium(II) catalytic effect on the coordinated acetonitrile hydrolysis  in basic solutions of near 1000 ? respect to the free ligand ? has been found. The value of the hydrolysis rate constant at 25 °C is ca. 4 times smaller than that corresponding to [Ru(trpy)(bpy)(CH3CN)]2+ (trpy = 2,2?:6?,2?-terpyridine), due to the steric constraints imposed by the facial geometry of coordinated tpm, as confirmed by X-ray structu4ral data. Besides, the activation entropy of this hydrolysis is highly negative and lower than that of the analogous trpy species.