Nitrile Hydrolysis in a Rhenium(I)-Ruthenium(III) Dinuclear Complex

FAGALDE, FLORENCIA; MELLACE, MARÍA G.; LIS DE KATZ, NOEMÍ D.; KATZ, NÉSTOR E.

JOURNAL OF COORDINATION CHEMISTRY

Taylor & Francis Group

Lugar: EE.UU ?/; Año: 2004 vol. 57 p. 635 - 639

0095-8972

We report kinetic data for the hydrolysis reaction: [(CO)3(bpy)ReI(4-CNpy)RuIII(NH3)5)]4++ H2O  [(CO)3(bpy)ReI(4-C(O)NHpy)RuIII(NH3)5)]4+ (bpy = 2,2?-bipyridine, 4-CNpy =4-cyanopyridine and 4-C(O)NHpy = isonicotinamido) , that occurs after formation of the mixed-valent complex [(CO)3(bpy)ReI(4-CNpy)RuIII(NH3)5]4+ in aqueous solution by oxidation with S2O82- of the dinuclear species [(CO)3(bpy)ReI(4-CNpy)RuII(NH3)5)]3+ .The observed rate constant, kh = 8.6 x10-3 s-1 , at 25 ºC, pH=3.0 (CF3COOH) and I =0.1M (KCl), is ca. 3 times higher than the corresponding one for the mononuclear complex [(4-CNpy)RuIII(NH3)5]3+ , indicating that the catalytic effect of a RuIII(NH3)5 moiety is enhanced by coordination of the free N of 4-CNpy to a ReI(CO)3(bpy) moiety. The value of kh is even higher than that of the dinuclear complex [(tpy)(bpy)RuII(4-CNpy)RuIII(NH3)5]5+ (tpy = 2,2?:6?,2?-terpyridine) pointing the fact that -backbonding from the ReI(CO)3(bpy) group to 4-CNpy is lower than that of the RuII(tpy)(bpy) group to 4-CNpy, which can be attributed to the fact that carbonyls are much stronger -acceptors than polypyridines.