Synthesis, Characterizations, and Catalytic Activity of a Cubic [Mo₃S₄Pd] Cluster Bearing Bulky Cyclopentadienyl Ligands

A cubic metal-sulfur cluster containing three Mo ions and a Pd ion, [CpSiEt33Mo3S4Pd]Cl (Mo3Pd, CpSiEt3 = C5Me4SiEt3), was synthesized by the incorporation of the Pd ion into a Mo3S4 cluster [CpSiEt33Mo3S4] (Mo3). Mo3Pd was characterized by 1H NMR, UV-vis, X-ray crystallography, and cyclic voltammetry measurements. The electrochemical measurements demonstrated reversible one- and two-electron reduction processes for Mo3Pd, which suggested potential catalytic activity for two-electron substrate reductions such as hydrogen evolution reaction. Controlled potential electrolysis in the presence of Mo3Pd and trifluoroethanol in THF solvent displayed H2 formation with a constant current over 60 min. The amount of generated H2 by Mo3Pd was two times higher than Mo3, indicating the catalytic activity facilitated by the Pd center. The mechanism of the catalytic cycle was determined by density functional theory