Aurophilicity at Sulfur Centers. Synthesis and Reactivity of the Complex [S(Au2dppf)]; Formation of Polynuclear Sulfur-Centered Complexes. Crystal Structures of [S(Au2dppf)]·2CHCl3, [(μ-Au2dppf){S(Au2dppf)}2](OTf)2· 8CHCl3, and [S(AuPPh2Me)2(Au2dppf)](ClO4)2·3CH2Cl2

Abstract

Treatment of [Au2Cl2(μ-dppf)] (dppf = 1,1‘-bis(diphenylphosphino)ferrocene) with Li2S (molar ratio 1:1) in ethanol gives a yellow solid [S(Au2dppf)] (1). The sulfur atom in complex 1 can coordinate several neutral or cationic gold(I) fragments giving the trinuclear neutral [S{Au(C6F5)}(Au2dppf)] (2) or cationic derivatives [S(AuL)(Au2dppf)]ClO4 [L = CH2PPh3 (3), PPh3 (4), PPh2Me (5)]. A pentanuclear complex [Au{S(Au2dppf)2}]ClO4 (6) is obtained by reaction of 2 equiv of complex 1 with 1 equiv of [Au(tht)2]ClO4, in which the central gold atom is bonded to two sulfur atoms. Treatment of compound 1 with [Au2(OTf)2(μ-dppf)] (OTf = trifluoromethylsulfonate) in a molar ratio 2:1 affords the hexanuclear complex [(μ-Au2dppf){S(Au2dppf)}2](OTf)2 (7), in which two SAu3 units are joined through the dppf ligand. The reaction of 1 with 2 equiv of [Au(OClO3)PR3] leads to the quadruply bridging derivatives [S(AuPR3)2(Au2dppf)](ClO4)2 [PR3 = PPh3 (8), PPh2Me (9)]. Crystal structure determinations were performed for complexes 1, 7, and 9. [S(Au2dppf)] (1) crystallizes in the monoclinic space group P2/n, with a = 12.571(4) Å, b = 10.579(4) Å, c = 15.212(4) Å, β = 107.84(3)°, Z = 2, T = −130 °C. [(μ-Au2dppf){S(Au2dppf)}2](OTf)2 (7) is triclinic, P1̄, with a = 15.177(3), b = 18.408(4), c = 27.894(8) Å, α = 88.83(2), β = 84.46(2), γ = 67.78(2), Z = 2, T = −100 °C. [S(AuPPh2Me)2(Au2dppf)](ClO4)2 (9) is triclinic, P1̄, with a = 13.727(2) Å, b = 15.952(3) Å, c = 17.763(2) Å, α = 71.738(12)°, β = 73.264(14)°, γ = 75.96(2)°, Z = 2, T = −100 °C. All three complexes display short gold(I)−gold(I) interactions.