EPR Detection and Characterisation of a Paramagnetic Mo(iii) Dihydride Intermediate Involved in Electrocatalytic Hydrogen Evolution

EPR spectroscopy and theoretical data show that the slow heterogeneous electron-transfer kinetics associated with the reduction of an 18-electron Mo(iv) acetato dihydride are a consequence of an η2–η1 rearrangement of the carboxylate ligand which gives a unique paramagnetic 17-electron Mo(iii) dihydride.