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 κ2C,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.