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(Ph 2 PC 6 H 4 S−CH = CH 2 )(Py)] + ( 2 ), which exhibits intriguing reactivity toward C 2 H 2 and H 2 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 H 2 to the cationic Mo(II) center, resulting in a Mo(IV) dihydride intermediate. Moreover, complex 2 also shows catalytic activity toward C 2 H 2 , leading to the production of polyacetylene and the extension of the vinylthioether ligand into a pendant triene chain.