Structures of Solvated Cations of Palladium(II) and Platinum(II) in Dimethyl Sulfoxide, Acetonitrile and Aqueous Solution Studied by EXAFS and LAXS

X-Ray absorption edge and EXAFS spectra of the solvated cations of platinum(II) in water, dimethyl sulfoxide and acetonitrile and of palladium(II) in dimethyl sulfoxide have been recorded and analyzed. The cations are four-coordinated. Pt-O in Pt(H2O)4(2+) is 2.01(1) angstrom and Pt-N in Pt(CH3CN)4(2+) is 2.00(1) angstrom. The dimethyl sulfoxide solvated cations of both platinum and palladium contain two sulfur- and two oxygen-bonded ligands with Pt-O 2.07(2), Pt-S 2.21(2), Pd-O 2.04(2), and Pd-S 2.23(2) angstrom, probably in a square-planar cis-arrangement, as in the solid state. Large-angle X-ray scattering (LAXS) studies of the platinum(II) dimethyl sulfoxide solvated cation in a solution of the triflate salt gave Pt-O 2.07(1) and Pt-S 2.20(1) angstrom and in a solution of the tetrafluoroborate salt Pt-O 2.07(2) and Pt-S 2.21(5) angstrom, in good agreement with the EXAFS results. Neither technique gave any support for axially bound solvent molecules in addition to the four in the assumed square coordination plane.