1,2-bis-N-[2′-(diphenylphosphanyl)benzoyl]diaminobenzene, a new chelating ligand with versatile coordination properties

1, 2-Bis-N-[2'-(diphenylphosphanyl) benzoyl]diamino-benzene (dppbH; 1) 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, 1 reacts with [MCl2(cod)] (M = Pd, Pt; cod = cyclooctadiene) to form square-planar complexes. However, in the case of palladium [PdCl2(dppbH)] (2) is obtained, while in the case of platinum [Pt(dppb)] (3) is formed. Thus, the nature of the metal induces a completely different coordination mode: In 2, the dppbH ligand only coordinates through the two phosphorus atoms, while in 3 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 2 to contain the two phosphorus atoms in a trans coordination mode and 3 to contain the two phosphorus atoms in a cis coordination mode. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).