Organometallic Chemistry in Aqueous Solution. Hydration of Nitriles to Amides Catalyzed by a Water-Soluble Molybdocene, (MeCp)2Mo(OH)(H2O)+

[Cp‘ 2 Mo(μ-OH) 2 MoCp‘ 2 ] 2+ ( 1 ) (Cp‘ = η 5 -CH 3 C 5 H 4 ) is a precatalyst for the hydration of nitriles in aqueous solution under mild conditions (∼80 °C). Among the nitriles hydrated were acetonitrile, isobutyronitrile, benzonitrile, 3-hydroxypropionitrile, 3-bromopropioamide, 4-cyanopyridine, succinonitrile, methyl cyanoacetate, 2-methoxyacetonitrile, and acrylonitrile. Except in the case of 2-methoxyacetonitrile, hydrolysis of the resulting amide products did not occur. Hydration of the C C double bond did not occur in acrylonitrile, but hydrolysis of ester and ether linkages did occur in nitriles containing those functional groups. The apparent rate constants and turnover frequencies of the catalytic reactions were determined using an iterative kinetics-fitting program. The rates and turnover frequencies are comparable to those reported for many homogeneous nitrile hydration catalysts described in the literature. In aqueous solution, 1 is in equilibrium with [Cp‘ 2 Mo(OH)(H 2 O)] + ( 2 ), and this monomer is proposed to be the active hydration catalyst. The hydration is proposed to occur by an intramolecular attack of a hydroxide ligand on a coordinated nitrile. The hydration reaction is irreversibly inhibited by product and reversibly inhibited by substrate (nitrile).