The reaction of the three-coordinate complex [Au{o-(PPh(2))(2)C2B10H10}tht]ClO4 (tht = tetrahydrothiophene) with diphosphines such as Ph(2)PCH(2)CH(2)PPh(2) (dppe), o-Ph(2)PC(6)H(4)PPh(2) (dppph), or cis-Ph(2)PCH=CHPPh(2) (dppey) afforded the mixed four-coordinate gold(I) complexes [Au(P-P)(P’-P’)]ClO4. The same reaction was also investigated with the diphosphine disulfides SPPh(2)NHPPh(2)S (SdppaS) and SPPh(2)CH(2)PPh(2)S (SdppmS) and led to the mixed compounds [Au(P-P)(S-S)]ClO4. All the complexes exhibit exceptionally high thermodynamic and kinetic stabilities in solution. The structure of the complex [Au{o-(PPh(2))(2)C2B10H10}{(SPPh(2))(2)CH2}]ClO4 has been determined by X-ray diffraction. It crystallizes in the monoclinic space group P2(1)/n with cell constants a = 13.271(3) Angstrom, b = 20.766(5) Angstrom, c = 20.517(4) Angstrom, beta = 95.50(2)degrees, and Z = 4. The gold atom exhibits tetrahedral coordination involving two phosphorus and two sulfur atoms, with Au-P = 2.380, 2.389(2) Angstrom and Au-S = 2.485, 2.661(2) Angstrom; the bite angles are P-Au-P = 89.72(6)degrees and S-Au-S = 95.32(5)degrees.