Gold(I) halide complexes of bis(diphenylphosphine)diphenyl ether ligands: a balance of ligand strain and non-covalent interactions.

A series of bis(gold(I) halide; halide = Cl, Br, I) complexes of di(phosphino)diphenyl ether derivatives (L = DPEphos, DBFphos, Xantphos, tBuXantphos) have been synthesized. The new complexes have been characterized by X-ray crystallography, multinuclear NMR, and elemental analysis. The compounds luminesce at room temperature in dichloromethane solution. Many such complexes undergo aurophilic Au...Au bonding, and have chiral structures as a result. In complexes of the tBuXantphos ligand, X-ray crystallography indicates that an ion pair forms where the diphosphine ligand chelates one gold atom, and the other is part of an [AuX(2)](-) counterion (X = Cl, Br, I). It appears that the observed conformations of the metal-coordinated ligands are a balance of ligand strain and non-covalent interactions, including aurophilicity, intramolecular pi-stacking, halide-halide repulsion, and intramolecular Au-O interactions. Together with previous investigations, this research shows that Xantphos and its derivatives form a robust set of coordination complexes with gold that are stable in air and amenable to further synthetic manipulation. It is anticipated that these materials will be suitable precursors for gold-carbon coupling reactions and gold-based catalysis.