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.