Benzimidazolin-2-ylidene Complexes of Palladium(II) Featuring a Thioether Moiety: Synthesis, Characterization, Molecular Dynamics, and Catalytic Activities

Six benzimidazolin-2-ylidene palladium­(II)
complexes with an alkyl–alkyl
thioether moiety in the side chain have been synthesized. Due to the
hemilabile metal–sulfur bond, the complexes exhibit a marked
fluxionality, as evidenced by NMR studies. The thioether moiety is
readily displaced by pyridine as well as by another NHC ligand. Hetero­(bis)-NHC
complexes formally derived from all six chelating mono-NHC complexes
have been synthesized as well. For both series of complexes, the catalytic
activity has been explored, and they were found to be active catalysts
for the intermolecular hydroamination reaction between a sterically
hindered aniline and an alkyne in the presence of triflic acid. Furthermore,
the complexes catalyze the direct arylation of 1-methylpyrrole.