CRYSTAL-STRUCTURES OF TRIORGANOPHOSPHINEGOLD(I) O-CYCLOHEXYLDITHIOCARBONATES - R3PAU(S2CO-C-C6H11), R = ET, PH AND C-HEXYL

The crystal structures of the title compounds R3PAu(S2CO-c-C6H11), R = Et, Ph and c-hexyl, have been determined at room temperature. Monoclinic crystals of the R = Et compound have space group C2/c with unit cell dimensions a = 26.754(4) angstrom, b = 7.264(1) angstrom, c = 18.928(3) angstrom, beta = 102.04(1)-degrees, Z = 8 and D(x) = 1.811 Mg m-3. Crystals of the R = Ph structure are triclinic with space group P1BAR and unit cell dimensions a = 11.372(2) angstrom, b = 13.053(6) angstrom, c = 9.488(3) angstrom; alpha = 109.45(3)-degrees, beta = 99.19(2)-degrees, gamma = 106.28(3)-degrees, Z = 2 and D(x) = 1. 722 Mg m-3. The R = c-hexyl compound crystallizes in the orthorhombic space group P2(1)2(1)2(1) with unit cell dimensions a = 8.121 (1) angstrom, b = 11. 108(4) angstrom, c = 30.212(5) angstrom, Z = 4 and D(x) = 1.591 Mg m-3. The structures were refined by a full-matrix least-squares procedure on 1908 reflections to final R = 0.039 for the R = Et compound, 3664 reflections and R = 0.055 for R = Ph and 1501 reflections and R = 0.040 for R = c-hexyl. The Au atom in each of the structures is linearly coordinated by the S atom, derived from a monodentate xanthate ligand, and the P atom. Different orientations of the xanthate ligands results in two structural forms. For the R = Et and Ph compounds the 0 atom is in close proximity of the Au atom whereas for the R = c-hexyl compound the S atom is orientated towards the Au atom. The different structures are rationalized in terms of the steric demands of the phosphine ligands. A close Au ... Au interaction of 3.120(1) angstrom is found in the R = Et compound; no such contacts are observed in the R = Ph and c-hexyl structures.