The First Phenanthrene-Fused Imidazol-2-ylidene and Its Transition-Metal Complexes

A new phenanthrene-fused N-heterocyclic carbene was generated and characterized in solution. The synthesis of air-stable Rh, Ir, and Ag complexes, supported by the new phenanthrene-fused imidazol-2-ylidene ligand, is described. Deprotonation of phenanthrene-fused imidazolium salt 4 in the presence of [M(COD)Cl]2 (M = Rh, Ir) afforded complexes 6 and 7 in excellent yields. The silver complex was obtained by reaction of 4 with Ag2O. The solid state molecular structures of these complexes have been determined by X-ray diffraction studies. The fluorescence emission spectra of 4, 6, and 7 are compared to that of phenanthrene.