Synthesis and characterization of gold(I) complexes with a triphosphine ligand having a bent trinuclear core interacted with a halide anion

The reaction of [AuCl(PPh3)] with bis(diphenylphosphinomethyl)phenylphosphine (dpmp) in a 3:2 ratio in the presence of NH4PF6 afforded the trinuclear gold(I) complex, [Au3(μ-dpmp)2Cl](PF6)2 (6), in good yield. Complex 6 was readily transformed, by treatment with 1 equiv. of KX (X=Br, I) in a methanol/dichloromethane mixed solvent, into the analogous complexes [Au3(μ-dpmp)2X](PF6)2 (X=Br (7), I (8)). Complexes 6–8 were characterized by elemental analysis, IR, 31P{1H} NMR, and UV–Vis absorption spectroscopic techniques and X-ray crystallographic analysis. Complexes 6–8 consist of three Au(I) ions bridged by two dpmp ligands (av. AuAu=2.944 Å (6), 2.950 Å (7), 2.934 Å (8)), which further interacted with a halide anion leading to a bent trinuclear core with AuAuAu angles 143.46(4)° (6), 141.12(6)° (7), and 142.73(5)° (8). The bent trimetallic core is assumed to be retained even in solution on the basis of their spectral data, and in particular, emission spectra were entirely different depending on the halide anion; complexes 6 (X=Cl) and 8 (X=I) were luminescent with emission band maxima at 469 and 551 nm, respectively, whereas complex 7 (X=Br) was not luminescent. The present results demonstrated that the structures and properties of dpmp-bridged trigold(I) complexes were dramatically influenced by the halide anions used.