GRAPHICAL ABSTRACT
Abstract
1H-1,3-Benzazaphospholes are aromatically stabilized σ2P heterocycles1,2 with increased π-density at phosphorus. This is caused by delocalization of the σ3N lone pair in the five-membered ring and disfavors π-back bonding from d10 transition metal cations to the ligand within the ring plane. The crystal structures of benzazaphosphole AgCl2c and CuX complexes2f display unusual bent or μ-bridging coordination although σ2P-phosphabenzene (phosphinine) ligands typically coordinate CuX groups in the σ-mode within the ring plane.3 Exceptions are complexes with pyridyl-phosphinine pincer ligands4a or 2-hydroxyphosphinines that acquire increased π-density by the +M-effect of the hydroxy group in o-position.4b