A Molecular Planetarium: Evidence for an Iodide Ligand Orbiting Two Gold(I) Ions in the Luminescent Cation, [Au2(μ-1,2-Bis(diphenylphosphino)methane)2I]+

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High Resolution Image Download MS PowerPoint Slide Four new crystalline gold(I) complexes, [Au 2 (μ-dppm) 2 I][Au 2 (μ-dppm) 2 (μ-I)](AsF 6 ) 4 ·4CH 2 Cl 2 ( 1 ), [Au 2 (μ-dppm) 2 (μ-I)]I·2CH 2 Cl 2 ( 2 ), [Au 2 (μ-dppm) 2 (μ-I)](PF 6 )·CH 2 Cl 2 ( 3 ), and [Au 2 (μ-dppm) 2 ](AsF 6 ) 2 ·CH 2 Cl 2 ( 4 ) where dppm is bis(diphenylphosphino)methane) have been prepared and structurally characterized by single crystal X-ray diffraction and nuclear magnetic resonance spectroscopy (NMR). Yellow crystals of [Au 2 (μ-dppm) 2 (μ-I)]I·2CH 2 Cl 2 ( 2 ) and [Au 2 (μ-dppm) 2 (μ-I)](PF 6 )·CH 2 Cl 2 ( 3 ) have a structure with two three-coordinate gold(I) ions held in close proximity by the dppm and bridging iodide ligands. Crystals of [Au 2 (μ-dppm) 2 I][Au 2 (μ-dppm) 2 (μ-I)](AsF 6 ) 4 ·4CH 2 Cl 2 ( 1 ) have two different cations: one similar to complexes 2 and 3 and the other cation with a terminal iodide ligand in an unusual arrangement that binds a two-coordinate gold(I) ion to a three-coordinate gold(I) ion through an aurophilic interaction. In contrast, [Au 2 (μ-dppm) 2 ](AsF 6 ) 2 ·CH 2 Cl 2 ( 4 ) has no anion bound and only has the gold ions as two-coordinate centers. Each complex displays luminescence under UV irradiation in the solid and solution states. Remarkably, the NMR spectra of solutions of the iodide complexes ( 1 ), ( 2 ), and ( 3 ) suggest that the iodide ion is bound to the [Au 2 (μ-dppm) 2 ] 2+ core but is able to circulate around this core.