1,2-Bis-<i>N</i>-[2’-(diphenylphosphanyl)benzoyl]diaminobenzene, a New Chelating Ligand with Versatile Coordination Properties

1,2-Bis-<i>N</i>-[2’-(diphenylphosphanyl)benzoyl]diaminobenzene (dppbH; <b>1</b>) was prepared by peptidic coupling and shown to exist, in the solid state, in the form of hydrogen-bonded dimers by single-crystal X-ray structure analysis. As expected, <b>1</b> reacts with [MCl₂ (cod)] (M = Pd, Pt; cod = cyclooctadiene) to form square-planar complexes. However, in the case of palladium [PdCl₂ (dppbH)] (<b>2</b>) is obtained, while in the case of platinum [Pt(dppb)] (<b>3</b>) is formed. Thus, the nature of the metal induces a completely different coordination mode: In <b>2</b>, the dppbH ligand only coordinates through the two phosphorus atoms, while in <b>3</b> a dppb ligand, formed by deprotonation of the two amino functions in dppbH, coordinates through the two phosphorus atoms and through the two nitrogen atoms. The single-crystal X-ray analyses of the two square-planar complexes reveal <b>2</b> to contain the two phosphorus atoms in a trans coordination mode and <b>3</b> to contain the two phosphorus atoms in a cis coordination mode.