Synthesis of NHC Complexes with an N-(2-Oxopropyl) Group

The unsymmetrically N,N'-substituted NHC precursor N-(2-oxopropyl),N'-picolylbenzimidazolium chloride (H-1)Cl, featuring an N-protecting group has been prepared. Reaction of (H-1)Cl with Ag2O followed by transmetallation of the NHC to [MCl2(Cp*)](2) (M=Rh, Ir) yielded complexes [MCl(Cp*)(kappa(2)-1)]Cl (M=Rh, [2]Cl; M=Ir, [3]Cl) with a chelating coordinated C-NHC perpendicular to N-pyridine ligand. Anion exchange gave complexes [2]BF4 (M=Rh) and [3]BF4 (M=Ir). Transmetallation of the NHC ligand from silver(I) to gold(I) gave the mononuclear complex [AuCl(1)] [4] bearing a monodentate, N-picoly funtionalized NHC ligand. Complex [4] reacts with AgBF4 to yield the dinuclear complex [5](BF4)(2) featuring two bridging mu(2)-C-NHC perpendicular to N-pyridine ligands. The molecular structures of [2]BF4 . CH2Cl2 and [3]BF4 . CH2Cl2 have been determined by X-ray diffraction studies.