An N-Heterocyclic Carbene Ligand with an Oxalamide Backbone

The preparation of the novel N-heterocyclic carbene ligand 3 based on an oxalamide backbone is described. Carbene 3 is not stable as a monomeric species at ambient temperature but dimerizes to the olefin 4 in the absence of trapping reagents. Carbene 3 reacts with elemental sulfur, tert-butylisocyanide, or [M(COD)Cl]2 (M = Rh, Ir) to give thione 5, ketenimine 6, or complexes [(3)M(COD)Cl] (7), respectively. The dicarbonyl complexes [(3)M(CO)2Cl] (8) (M = Rh, Ir) show high-energy CO vibrations. The carbene ligand 3 behaves as a remarkably poor net electron donor compared to other NHC ligands.