Aqueous "green" organometallic chemistry: Structure of the molybdocene monohydride used for carbonyl reduction in water

The compound bis(eta (5)-cyclopentadienyl)hydridomolybdenum(IV) triflate, w hich was synthesized from Cp2MoH2 and methyl triflate, is water soluble and undergoes hydride deuteride exchange in D2O. The molybdocene monohydride r educes ketones and aldehydes in water under mild aqueous conditions (pH 7 a nd 40 degreesC), which underscores the utility of this metallocene hydride for further organic transformations. Mechanistic features for the ketone -- > alcohol reduction suggest that either the reduction process is promoted b y acid protonation of the carbonyl oxygen or it follows the reverse pathway of the aqueous C-H activation of primary alcohols by Cp2MoCl2(aq) reported earlier by Balzarek and Tyler.