Catalytic hydrogenation of olefins by a multifunctional molybdenum-sulfur complex

Exploration of molybdenum complexes as homogeneous hydrogenation catalysts has garnered significant attention, but hydrogenation of unactivated olefins under mild conditions are scarce. Here, we report the synthesis of a molybdenum complex, [Cp*Mo(Ph₂PC₆H₄S-CH = CH₂)(Py)]⁺ (2), which exhibits intriguing reactivity toward C₂H₂ and H₂ under ambient pressure. This vinylthioether complex showcases efficient catalytic activity in the hydrogenation of various aromatic and aliphatic alkenes, demonstrating a broad substrate scope without the need for any additives. The catalytic pathway involves an uncommon oxidative addition of H₂ to the cationic Mo(II) center, resulting in a Mo(IV) dihydride intermediate. Moreover, complex 2 also shows catalytic activity toward C₂H₂, leading to the production of polyacetylene and the extension of the vinylthioether ligand into a pendant triene chain.