Assembly and Redox-Rich Hydride Chemistry of an Asymmetric Mo(2)S(2) Platform

Although molybdenum sulfide materials show promise as electrocatalysts for proton reduction, the hydrido species proposed as intermediates remain poorly characterized. We report herein the synthesis, reactions and spectroscopic properties of a molybdenum-hydride complex featuring an asymmetric Mo(2)S(2) core. This molecule displays rich redox chemistry with electrochemical couples at E(½) = −0.45, −0.78 and −1.99 V vs. Fc/Fc(+). The corresponding hydrido-complexes for all three redox levels were isolated and characterized crystallographically. Through an analysis of solid-state bond metrics and DFT calculations, we show that the electron-transfer processes for the two more positive couples are centered predominantly on the pyridinediimine supporting ligand, whereas for the most negative couple electron-transfer is mostly Mo-localized.