Bis(N-heterocyclic carbene)s incorporating silicon in the ligand backbone†

A straightforward, modular, and high yielding synthetic protocol for accessing bis(N-heterocyclic carbene)s incorporating alkyl and aryl N-substituents with varied steric profiles, as well as flexible dimethylsilane and dimethylsiloxane linkers is presented. This provides a more direct entry to both new and reported chelating bis(carbene) ligands. The incorporation of dimethylsilicon fragments rather than linear alkyl chains in the linker is expected to enhance the chelating properties of the ligand by means of the Thorpe–Ingold effect.