CRYSTAL AND MOLECULAR-STRUCTURES OF TRI(O-TOLYL)PHOSPHINEGOLD(I) O-ALKYLDITHIOCARBONATES - O-TOL(3)PAU(S(2)COR), R=PR-I AND CH(2)CH(2)OME

The crystal structures of the title compounds o-tol(3)PAu((S2COPr)-Pr-i), C25H28AuOPS2, and o-tol(3)PAu(S(2)COCH(2)CH(2)OMe), C25H28AuO2PS2, have been determined at room temperature. The colorless crystals of o-tol(3)PAu(S2COiPr) are monoclinic, space group P2(1)/c, with unit cell dimensions a = 14.277(5) Angstrom, b = 12.716(5) Angstrom, c = 14.829(2) Angstrom, beta = 115.23(1)degrees, Z = 4 and D-x = 1.736 Mg m(-3) and the pale-yelrow crystals of o-tol(3)PAu(S(2)COCH(2)CH(2)OMe) are triclinic, space group P (1) over bar, with dimensions a = 11.209(4) Angstrom, b = 13.195(5) Angstrom, c = 9.046(3) Angstrom, alpha = 107.05(3)degrees, beta = 91.78(3)degrees and gamma = 74.40(3)degrees, Z = 2 and D-x = 1.761 Mg m(-3).The structures were solved by direct-methods and each refined by a full-matrix least-squares procedure to final R = 0.041 (0.041) using 2887 (3841) reflections, respectively. The gold atom in each of the structures exists in a linear geometry defined by the S atom, derived from a monodentate xanthate Iigand, and the phosphine P atom. The major difference between the two molecules is found in the orientation of the xanthate ligand. In the structure of o-tol(3)PAu((S2COPr)-Pr-i) the O atom is directed towards the Au atom, i.e. a 'S, O' conformation, such that the Au ... O separation is 2.892(7) Angstrom, by contrast, in the structure of o-tol(3)PAu(S(2)COCH(2)CH(2)OMe) a close intramolecular Au ... S contact of 3.347(3) Angstrom is found; the 'S, S' confermation. A variable-temperature multinuclear magnetic resonance (H-1 and P-31) Study did not show the presence of both S, O and S, S conformations co-existing in solution for either of the compounds.