Benzonitrile hydrolysis catalyzed by a ruthenium(II) complex

Abstract

The rate constant for the basic hydrolysis of benzonitrile (PhCN) to benzamide (PhCONH2) in the [RuII(tpy)(bpy)] moiety (tpy = 2,2′:6′,2″-terpyridine, bpy = 2,2′-bipyridine) (kOH = 3.7 × 10-2 M-1s-1) is 5 × 103 times higher than that of the free ligand and two times higher than that corresponding to the analogous acetonitrile complex. This effect is unusual for a transition metal in the (II) oxidation state, and can be attributed to the π-electron acceptor properties of both the polypyridyl ligands and the phenyl group. Since amides, being poor π-acceptor ligands, are rapidly released from the coordination sphere of ruthenium(II), the final product of this process is the [Ru(tpy)(bpy)(OH)]+ complex. The activation parameters for this nitrile hydrolysis have been determined and compare reasonably well with other values for similar reactions.