Different coordination modes of 2-(diphenylphosphino)azobenzenes in complexation with hard and soft metals.

Control of coordination modes of a ligand in metal complexes is significant because the coordination modes influence catalytic properties of transition metal catalysts. Reactions of 2-diphenylphosphinoazobenzenes, which are in equilibrium with the inner phosphonium salts, with ZnCl(2), W(CO)(5)(THF), and PtCl(2)(cod) gave three different coordination types of metal complexes with distinctive UV-vis absorptions. All the complexes were characterized by X-ray crystallographic analyses. In the zinc and tungsten complexes, the source molecule functions as an amide ligand and a phosphine ligand, respectively. In the platinum complex, the phosphorus molecule works as a tridentate ligand with formation of a carbon-platinum bond.