Aurophilicity at sulfur centers. Synthesis of the polyaurated species [S(AuPR(3))(n)]((n-2)+) (n=2-6)

The reaction of two equivalents of [AuCl(PR(3))] with Li2S in ethanol leads to the dinuclear complexes [S(AuPR(3))(2)] (PR(3)=PPh(3), PPh(2)Me, P(p-Tol)(3)), which contain bridging sulfide ligands. These complexes can add AuPR(3)(+) fragments stepwise to form the cationic species [S(AuPR(3))3](+), [S(AuPR(3))(4)](2+), [S(AuPR(3))(5)](3+) and [S(AuPR(3))(6)](4+). The reaction of [S(AuPR(3))(2)] with different AuPR'(+)(3) fragments affords the mixed complexes [S(AuPR(3))(n)(AuPR'(3))(m)]((n+m-2)+) (n+m=5 or 6). The crystal structures of the complexes [S(AuPPh(2)Me)(3)](OTf) and [S(AuPPh(3))(4)](ClO4)(2) have been established by X-ray diffraction. [S(AuPPh(2)Me)(3)](OTf) : triclinic, space group P (1) over bar, a=11.547(4), b=12.750(5), c=15.355(6) Angstrom, a=97.55(3), beta=104.02(2), gamma=102.41(3)degrees, Z=2, T=-130 degrees C. In the crystal the cations are paired across symmetry centers with short intermolecular S ... Au and Au ... Au contacts. [S(AuPPh(3))(4)](ClO4)(2): monoclinic, space group P2(1)/n, a=18.028(10), b=29.23(2), c=18.183(10) Angstrom, beta=116.23(5)degrees, Z=4, T=-100 degrees C. The structure of the cation is square pyramidal, with the sulfur in the apical position; intramolecular gold-gold interactions are observed.