π-Rich σ2P-Ligands: Unusual Coordination Behavior of 1H-1,3-Benzazaphospholes Toward Late Transition Metals

Coordination chemical studies of 1H-1,3-benzazaphospholes, pi-excess aromatic sigma P-2-ligands, demonstrate similar ligand properties to those of phosphabenzenes toward M-VI(CO)(n) but marked differences toward nonzerovalent transition metals. Benzazaphosphole d(8)-metal halide complexes are more strongly destabilized and undergo consecutive reactions, whereas benzazaphosphole coinage metal halide and HgCl2 complexes generally display mu P-2- and/or bent eta P-1-coordination with pi-P donor bond contribution, contrasting with the preference of phosphinine CuX complexes for eta P-1-coordination within the ring plane.