Mechanistic aspects of the reaction of hydrogen sulfide with dinuclear palladium(I) complexes containing bis(diphenylphosphino)methane and related ligands

Abstract

Kinetic and low temperature nmr data are presented for the reaction of hydrogen sulfide with Pd 2 X 2 (μ-dpm) 2 species in dichloromethane solution (X = halide, dpm = bis(diphenylphosphino)methane. The reactions form the corresponding bridged-sulfide, A-frame complex via oxidative-addition of H 2 S across the Pd—Pd bond to give a hydrido(mercapto) intermediate, that subsequently liberates H 2 to give Pd 2 X 2 (μ-S) (μ-dpm) 2 species. Quantitative kinetic data showing first order behaviour in both Pd 2 dimer and H 2 S concentrations are given for the bromide system over the temperature range 0–35 °C, as well as more limited data for the photosensitive iodide system; plausible mechanisms are discussed. Some qualitative findings are presented for related systems containing 1, 1-bis(diphenylphosphino)ethane. Keywords: palladium complexes, hydrogen sulfide, bis(diphenylphosphino)methane.