Polynuclear gold complexes with bridging selenido ligands. Theoretical studies of gold-gold interactions

The compounds [Se(AuPPh3)(2)] and [Se(Au(2)dppf)] are good precursors for the synthesis of highly aurated selenium-centered derivatives. Thus the reaction of [Se(AuPPh3)(2)] with various molar ratios of [Au(OTf)PPh3] affords the homoleptic species [Se(AuPPh3)(n)](OTf)(n-2) (n = 3-6). Similarly, the treatment of [Se(Au(2)dppf)] with various stoichiometric ratios of [Au-2(OTf)(2)(mu -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(AuPPh3)(2)}(2)] ClO4 and [Au{Se(Au(2)dppf)}(2)] ClO4 have been obtained by reaction of the precursors with [Au(tht)(2)]-ClO4 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(AuPH3)(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.