Palladium and iridium complexes with a N,P,N-bis(pyridine) phenylphosphine ligand

A variety of Pd(II) complexes containing the neutral N,P,N-ligand bis(2-picolyl)phenylphosphine (NpyPNpy) have been synthesised and characterized by IR and NMR spectroscopy and X-ray diffraction. The neutral complex [PdCl2(NpyPNpy-N,P)] ( 1) has been selectively obtained in high yield by reaction of [PdCl2(NCPh)(2)] with the ligand in dichloromethane. The cationic complexes [PdCl(NpyPNpy-N, P, N)]PF6 ( 2) and [Pd(NpyPNpy-N,P,N)(NCMe)](PF6)(2) ( 5) have been prepared from the same reagents by addition to the reaction mixture of one or two equivalents of TlPF6, respectively. It was found that dynamic exchange of the pyridine rings of 1 occurs on the NMR time-scale and possible mechanisms are discussed. As a by-product of the synthesis of 2, the unexpected dinuclear complex [Pd2Cl2(mu-NpyPNpy)(2)](PF6)(2) ( 3) has been isolated in 10% yield. Its molecular structure in the solid state reveals the presence of two NpyPNpy chelating/bridging ligands. The cationic complex [Pd2Cl2(m-NpyPNpy)(2)](2+) was then selectively obtained by reaction of cis-[Pd(NpyPNpy-N, P)(2)](BF4)(2) ( 4) with [PdCl2(cod)]. H-1- and P-31{H-1} NMR studies have demonstrated that 3 converts slowly into 2 in DMSO solution. The Ir(I) complexes [IrCl(cod)(NpyPNpy)] (6) and [Ir(cod)(NpyPNpy-N, P, N)]BArF ( 7) have also been prepared, the latter exhibits a trigonal bipyramidal structure with the ligand displaying a facial coordination mode. Compound 7 represents a rare example of an Ir(I) complex bearing a N,P,N-chelating ligand.