Gold(I)-gold(III) interactions in polynuclear sulfur-centered complexes. Synthesis and structural characterization of [S(Au(2)dppf){Au(C6F5)(3)}] and [{S(Au(2)dppf)}(2){Au(C6F5)(2)}]OTf (dppf equals 1,1'-bis(diphenylphosphino)ferrocene)

The reactions of [S(Au(2)dppf)] (dppf = 1,1'-bis(diphenylphosphino)ferrocene) with the gold(III) precursors [Au(C6F5)(3)(OEt2)] and [Au(C6F5)(2)(OEt2)(2)]OTf afford the mixed-valence complexes [S(Au(2)dppf)(Au(C6F5)(3))] (1) and [{S(Au(2)dppf)}(2)(Au(C6F5)(2)}]OTf (2). The crystal structures of these derivatives have been determined and show short gold(I)-gold(III) contacts of 3.404(1) Angstrom in 1 and 3.2195(8) and 3.3661(10) Angstrom in 2. DFT calculations, including correlation and relativistic corrections, show that in these compounds where sulfur bridges three gold atoms it prefers to become pyramidal rather than planar, and Au(I)-Au(III) distances are indicative of a possible weak interaction. EH calculations suggest that such interaction is similar in origin to the well-studied Au(I)-Au(I) weak interactions and that it may occur in some real compounds.