Activation and Deactivation of Cp*Ir(TsDPEN) Hydrogenation Catalysts in Water

The addition of H3PO4 to (CpIr)-Ir-*(TsDPEN-H), where TsDPEN = H2NCHPhCHPhNTs-, is a simple method to obtain a water-soluble hydrogenation catalyst capable of reducing aromatic ketones to their corresponding alcohols in aqueous solutions. Key to the reactivity is the low affinity of the coordinatively unsaturated [Cp*Ir(TsDPEN)](+) for H2PO4-. Catalyst degradation proceeds via the protonation of the tosylamido ligand, as was established by the crystallographic characterization of the tosylamine complex [Cp*Ir(NCMe)(HTsDPEN)](2+). ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)