Transition metal complexes have been widely employed as homogenous catalysts for hydrogenation and related reduction chemistry, many of which require harsh conditions. Despite the inspiration from nature-optimized metal-sulfur complexes (i.e., nickel-iron hydrogenases) for hydrogen gas activation under mild conditions, a relatively small number of synthetic metal-sulfur variants have been reported. Experimental reports show that a series of so-called half-sandwich metal-sulfur complexes have been successful at facilitating hydrogenation and reduction. However, closer observation of the data reveals varied reactivity across the reported complexes, and little is known about the factors that control such deviations in catalyst effectiveness, limiting our ability to develop more optimal bioreminiscent catalysts. Density functional theory calculations were performed to investigate the likely mechanisms for the reduction (hydrogenation and hydrosilylation) of ketones mediated by half-sandwich iridium(III)-sulfur and rhodium(III)-sulfur complexes. Several computational model systems were employed to reveal the role of the metal, ligand coordination, and reducing agent on the energetically preferred mechanistic pathway. In this poster, insights from the computational work will be presented.

Catalytic reduction mechanisms mediated by half-sandwich iridium(III)- and rhodium(III)-sulfur complexes

ACS Spring 2022

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