SPECTROSCOPIC AND STRUCTURAL-PROPERTIES OF DIMETHYLSULFOXIDE, DIPHENYLSULFOXIDE AND METHYLPHENYLSULFOXIDE PLATINUM COMPLEXES - THE CRYSTAL AND MOLECULAR-STRUCTURES OF CIS-DICHLOROBIS(METHYLPHENYLSULFOXIDE)-PLATINUM(II) AND POTASSIUMTRICHLORO(PHENYLSULFOXIDE)PLATINUM(II)-ACETONE SOLVATE

The preparation and properties of platinum complexes with bulky sulfoxide ligands have been examined. The reaction of methylphenylsulfoxide (MePhSO) with K2PtCl4 gives as expected cis-[PtCl2(MePhSO)2] whereas the product with the more sterically demanding diphenylsulfoxide Ph2SO is K[PtCl3(Ph2SO)]. This monosulfoxide anion is also formed with methyltert-butylsulfoxide, Met-BuSO. The molecular structures of cis-[PtCl2(MePhSO)2] (IIA) and K[PtCl3(Ph2SO)].acetone (V) were resolved by X-ray diffraction. The crystals of Cis-[PtCl2(MePhSO)2] are monoclinic P2(1)/c with cell dimensions a = 9.1834(2), b = 15.7256(4), c = 12.4279(3) angstrom, beta = 106.78(2)-degrees and Z = 4. The structure was refined to R(w) = 4.86%. The sulfoxides are S-bound as expected and the meso (S,S configuration around the chiral sulfur atom) diastereomer was solved. All bond lengths and bond angles around the square planar platinum are normal with Pt-S distances of 2.244(3) and 2.238(3) angstrom. The Pt-Cl distances of 2.315(3) and 2.303(3) angstrom are within the range expected for Cl trans S. The phenyl groups of the MePhSO lie essentially perpendicular to the coordination plane with dihedral angles of 92.1 and 84.2-degrees. The crystals of K[PtCl3(Ph2SO)].acetone are also monoclinic P2(1)/c with a = 9.775(3), b = 8.239(2) and c = 24.974(6) angstrom, beta = 95.78(2)-degrees and Z = 4. Bond lengths and angles around the coordination plane are normal. The Pt-S distance is 2.214(3) angstrom and the Pt-Cl bond trans S is 2.327(3) angstrom, longer than the mutually trans Pt-Cl bonds 2.302(3) angstrom. The phenyl groups make dihedral angles of 81.8 and 100.9-degrees with the coordination plane and are essentially mutually perpendicular with a Ph-Ph dihedral angle of 92.9-degrees. The K cation has non-bonding contacts to both the sulfoxide and acetone oxygen atoms of 2.673(9) and 2.728(13)-degrees, respectively. The structural parameters are discussed with respect to data from Me2SO and sterically hindered sulfoxides. There are no major differences found in the structural parameters to explain the trends in reactivity of the various sulfoxides. Complementary studies using Pt-195 NMR spectroscopy show that the order of shielding in the series K[PtCl3(R'R"SO)] is Ph2SO > MePhSO > Me2SO. The values of the Pt-195 chemical shifts are discussed with respect to models of sulfoxide bonding to platinum.