Bridging 1,2-Bis(diphenylphosphino)methane\nLigands\nFacilitate the Formation of Binuclear Complexes with Both Two-Coordinate\nand Three-Coordinate Gold(I) Ions

Five new crystalline gold(I) complexes β-Au<sub>2</sub>(μ-dppm)<sub>2</sub>Br<sub>2</sub>·2CH<sub>2</sub>Cl<sub>2</sub> (<b>1</b>), [Au<sub>2</sub>(μ- dppm)<sub>2</sub>Br]Br·2CH<sub>2</sub>Cl<sub>2</sub> (<b>2</b>),\n[Au<sub>2</sub>(μ-dppm)<sub>2</sub>Br](PF<sub>6</sub>) (<b>3</b>), [Au<sub>2</sub>(μ-dppm)<sub>2</sub>Cl](BPh<sub>4</sub>)·3CH<sub>2</sub>Cl<sub>2</sub> (<b>4</b>) and [Au<sub>2</sub>(μ-dppm)<sub>2</sub>]Cl(AsF<sub>6</sub>)·2CH<sub>2</sub>Cl<sub>2</sub> (<b>5</b>) (where\ndppm is bis(diphenylphosphino)methane) have been prepared and structurally\ncharacterized by single crystal X-ray diffraction. Colorless β-Au<sub>2</sub>(μ-dppm)<sub>2</sub>Br<sub>2</sub>·2CH<sub>2</sub>Cl<sub>2</sub> (<b>1</b>) has centrosymmetric structure with\ntwo three-coordinate gold(I) ions held in close proximity by the dppm\nligands. Crystals of [Au<sub>2</sub>(μ- dppm)<sub>2</sub>Br]Br·2CH<sub>2</sub>Cl<sub>2</sub> (<b>2</b>), [Au<sub>2</sub>(μ-dppm)<sub>2</sub>Br](PF<sub>6</sub>) (<b>3</b>), and [Au<sub>2</sub>(μ-dppm)<sub>2</sub>Cl](BPh<sub>4</sub>)·3CH<sub>2</sub>Cl<sub>2</sub> (<b>4</b>) have a cation with an unusual arrangement that binds a\ntwo-coordinate gold(I) ion to a three-coordinate gold(I) ion through\nan aurophilic interaction. Whereas Au<sub>2</sub>(μ-dppm)<sub>2</sub>Cl(BPh<sub>4</sub>)·3CH<sub>2</sub>Cl<sub>2</sub> (<b>4</b>) has a chloride ion bound to only one of the gold ions in\nthe complex, [Au<sub>2</sub>(μ-dppm)<sub>2</sub>]Cl(AsF<sub>6</sub>)·2CH<sub>2</sub>Cl<sub>2</sub> (<b>5</b>) has\nan ion paired chloride ion that is symmetrically disposed between\nthe two gold ions at a rather long distance. Each complex displays\nluminescence under UV irradiation.