Polynuclear Gold Complexes with Bridging Selenido Ligands. Theoretical Studies of Gold−Gold Interactions

The compounds [Se(AuPPh 3 ) 2 ] and [Se(Au 2 dppf)] are good precursors for the synthesis of highly aurated selenium-centered derivatives. Thus the reaction of [Se(AuPPh 3 ) 2 ] with various molar ratios of [Au(OTf)PPh 3 ] affords the homoleptic species [Se(AuPPh 3 ) n ](OTf) n - 2 ( n = 3−6). Similarly, the treatment of [Se(Au 2 dppf)] with various stoichiometric ratios of [Au 2 (OTf) 2 (μ-dppf)] gives the polynuclear derivatives [(Au 2 dppf){Se(Au 2 dppf)} 2 ](OTf) 2, [Se(Au 2 dppf) 2 ](OTf) 2, and [Se(Au 2 dppf) 3 ](OTf) 4 . The compounds [Au{Se(AuPPh 3 ) 2 } 2 ]ClO 4 and [Au{Se(Au 2 dppf)} 2 ]ClO 4 have been obtained by reaction of the precursors with [Au(tht) 2 ]ClO 4 in a molar ratio of 2:1. Some of these derivatives have been characterized by X-ray diffraction studies and show unusual geometries, associated with gold−gold interactions. The latter have been studied theoretically using [Se(AuPH 3 ) n ] ( n - 2)+ ( n = 2−6) models at the HF and MP2 levels with quasi-relativistic pseudopotentials. There is a good agreement between experimental and theoretical geometries.