cis-Influence and trans-Influence on Bond Distances. Synthesis and Crystal Structures of the Bis(trifluoromethanesulfonates) of Tetrakis(dimethylsulfide)- and Tetrakis(1,4-thioxane)-platinum(II)

Crystals of [Pt{(CH3)2S}4](CF3SO3)2, M(r) = 741.76, and [Pt(C4H8OS)4](CF3SO3)2.H2O, M(r) = 927.93, were prepared by dissolution of platinum(II) hydroxide in solutions of trifluoromethanesulfonic acid in dimethyl sulfide and 1,4-thioxane, respectively. The structures were determined from X-ray intensity data (Mo K-alpha, lambda = 0.7107 angstrom) collected at room temperature with a CAD-4 diffractometer. The space group for the dimethylsulfide compound is P2(1)/c with a = 8.5630(8), b = 8.692(1), c = 16.360(3) angstrom, beta = 97.064(9)-degrees, V = 1208.4(2) angstrom 3, Z = 2, D(x) = 2.038 Mg m-3, F(000) = 720 and mu = 6.43 mm-1. The refinements converged to R = 0.025 for 1922 reflections with I > 3 sigma(I). The 1,4-thioxane compound crystallizes in the space group C2/c with a = 14.438(2), b = 13.016(2), c = 21.696(3) angstrom, beta = 126.32(1)degrees, V = 3285.0(6) angstrom 3, Z = 4, D(x) = 1.876 Mg m-3, F(000) = 1832 and mu = 4.76 mm-1. The refinements converged to R = 0.035 for 2268 reflections with I > 3-sigma(I). The coordination around platinum is square-planar with four sulfur donor ligands in both cases. In the dimethyl sulfide complex the two unique (CH3)2S groups are disordered. The sulfur atoms occupy two different positions with coinciding methyl carbon atoms. The platinum-sulfur distances are between 2.317(3) and 2.321(4) angstrom in the dimethylsulfide and between 2.318(2) and 2.321(2) angstrom in the thioxane complex. Packing forces thus have a negligible influence on these Pt-S distances, and the mean Pt-S distance of 2.319(2) angstrom is a suitable reference distance for calculation of the cis- and trans-influence by other donor atoms on the Pt-S bond in other complexes.