Bridging 1,2-Bis(diphenylphosphino)methane Ligands Facilitate the Formation of Binuclear Complexes with Both Two-Coordinate and Three-Coordinate Gold(I) Ions

Five new crystalline gold(I) complexes β-Au₂(μ-dppm)₂Br₂·2CH₂Cl₂ (<b>1</b>), [Au₂(μ- dppm)₂Br]Br·2CH₂Cl₂ (<b>2</b>), [Au₂(μ-dppm)₂Br](PF₆) (<b>3</b>), [Au₂(μ-dppm)₂Cl](BPh₄)·3CH₂Cl₂ (<b>4</b>) and [Au₂(μ-dppm)₂]Cl(AsF₆)·2CH₂Cl₂ (<b>5</b>) (where dppm is bis(diphenylphosphino)methane) have been prepared and structurally characterized by single crystal X-ray diffraction. Colorless β-Au₂(μ-dppm)₂Br₂·2CH₂Cl₂ (<b>1</b>) has centrosymmetric structure with two three-coordinate gold(I) ions held in close proximity by the dppm ligands. Crystals of [Au₂(μ- dppm)₂Br]Br·2CH₂Cl₂ (<b>2</b>), [Au₂(μ-dppm)₂Br](PF₆) (<b>3</b>), and [Au₂(μ-dppm)₂Cl](BPh₄)·3CH₂Cl₂ (<b>4</b>) have a cation with an unusual arrangement that binds a two-coordinate gold(I) ion to a three-coordinate gold(I) ion through an aurophilic interaction. Whereas Au₂(μ-dppm)₂Cl(BPh₄)·3CH₂Cl₂ (<b>4</b>) has a chloride ion bound to only one of the gold ions in the complex, [Au₂(μ-dppm)₂]Cl(AsF₆)·2CH₂Cl₂ (<b>5</b>) has an ion paired chloride ion that is symmetrically disposed between the two gold ions at a rather long distance. Each complex displays luminescence under UV irradiation.