Platinum(II) Complexes with Thioether-Functionalized Benzimidazolin-2-ylidene Ligands: Synthesis, Structural Characterization, and Application in Hydroelementation Reactions

A series of six benzimidazolium salts with an alkyl-alkyl thioether moiety in the side chain has been synthesized. While it was impossible to obtain the platinum(II) complexes by direct reaction between ligand precursors and basic platinum salts, the mild silver carbene transfer reaction gave the desired complexes in all cases. X-ray crystallography confirmed the expected kappa C-2,S coordination mode of the benzimidazolin-2-ylidene ligands, with a cis arrangement of the carbene and the hemilabile thioether moieties in all complexes. Preliminary studies of the catalytic activity of these complexes showed them to be active catalysts for the intermolecular hydroamination of alkynes with sterically hindered anilines in conjunction with silver triflate. Additionally, the complexes catalyzed the hydrosilylation of alkenes with excellent yields and good regioselectivity.