Synthetic, electrochmeical, and structural studies on heterobimetallic crown thioether complexes with Group 10 metals: the crystal structures of [Pt(9S3)(dppf)](PF_6)_2(centre dot)CH_3NO_2 and [Pd(9S3)(dppf)](PF_6)_2(centre dot)CH_3NO_2

摘要

The syntheses, electrochemistry, and crystal structures for two new Pt(II) and Pd(II) heteroleptic bimetallic complexes with the crown tithioether 1,4,7-trithiacyclononane (9S3) and the diphosphine ligand, 1,1'-bis(diphenylphosphino)ferrocene (dppf) are reported. Both complexes have the general formula [M(9S3)(dppf)](PF_6)_2 (M = Pt or Pd) and exhibit the anticipated structure forming a distoryted cis square planar array of two sulfur atoms from the 9S3 and two phosphorus atoms. These are, to our knowledge, the first reported examples of dppf transition metal complexes involving a thioether as the ancillary ligand. The dppf ligand functions as a bidentate chelator to a single metal center, and the third 9S3 sulfur atom does interact with the metal ion from a greater distance (Pt-S = 2.8167(8) A; Pd-S = 2.791(5) A) to yield an elongated square pyramidal geometry. The two structures are isomorphous with very similar bond distances and angles. The values for the ~(31)P-NMR chemical shifts (Pt = 15.09 ppm, Pd = -0.47 ppm), the ~(195)Pt-NMR chemical shift for the Pt(II) complex (-4353 ppm) and ~1J(~(195)Pt-~(31)P) coupling constants (3511 Hz) are all consistent with a cis-MS_2P_2 square planar coordination sphere. The 9S3 ligand is fluxional in solution for both complexes. The electrochemistry of both complexes is dominated by a reversible Fe(II)/Fe(III) couple from the ferrocene moiety (E_(1/2) = +721 mV for Pt(II), +732 mV for Pd(II), both versus Fc/Fc~+).