Synthesis of a novel pyridine-diamino bridged diphosphine ligand and its macrocyclic metal complexes

Abstract

A novel long chain diphosphine ligand with a pyridine-diamino bridge, 2,6-bis( N-benzyl- N-diphenylphosphinomethylamino)pyridine (PNP1), was prepared conveniently using the Mannich reaction of HPPh 2 with paraformaldehyde and 2,6-bis( N-benzylamino)pyridine in high yield. Reactions of the ligand with metal complexes, M(COD)Cl 2 (M = Pd, Pt), M(CH 3CN) 4ClO 4 (M = Cu, Ag) and M(CO) 6 (M = Mo, W) afforded the corresponding 10-numbered monometallic macrocyclic complexes with an uncoordinated pyridyl bridge. The monometallic chelate PdCl 2(PNP1) continued to react with Ag + or Cu + giving the μ-Cl bridged bicyclic metallic complex (μ-Cl) 2[PdCl(PNP1)] 2. The diphenylphosphine group coordinated with metal ion in cis-form in all the 10-numbered macrocyclic metal complexes. Ligand PNP1 and another known analogous 2,6-bis( N-diphenylphosphinoamino)pyridine (PNP2) reacted with Au(SMe 2)Cl giving the corresponding bimetallic Au 2Cl 2(PNP1) and Au 2Cl 2(PNP2), respectively. The latter bimetallic complexes continued to react with Ag + and diphosphine ligand to give the corresponding bimetallic macrocyclic complexes Au 2(ligand) 2(ClO 4) 2. All the complexes were characterized and the structures of some complexes were confirmed by X-ray single crystallography determination.