One-Pot Catalytic Cleavage of C═S Double Bonds by Pd Catalysts at Room Temperature

Abstract

The C═S double bonds in CS₂ and thioketones were catalytically cleaved by Pd dimeric complexes [(N^∧N)₂Pd₂(NO₃)₂](NO₃)₂ (N^∧N, 2,2'-bipyridine, 4,4'-dimethylbipyridine or 4,4'-bis(trifluoromethyl)) at room temperature in one pot to afford CO₂ and ketones, respectively, for the first time. The mechanisms were fully investigated by kinetic NMR, isotope-labeled experiments, in situ ESI-MS, and DFT calculations. The reaction is involved a hydrolytic desulfurization process to generate C═O double bonds and a trinuclear cluster, which plays a pivotal role in the catalytic cycle to regenerate the dimeric catalysts with HNO₃. Furthermore, the electronic properties of catalyst ligands possess significant influence on reaction rates and kinetic parameters. At the same temperature, the reaction rate is consistent with the order of electronegativity of N^∧N ligands (4,4'-bis(trifluoromethyl) > 2,2'-bipyridine > 4,4'-dimethylbipyridine). This homogeneous catalytic reaction features mild conditions, a broad substrate scope, and operational simplicity, affording insight into the mechanism of catalytic activation of carbon sulfur bonds.