Synthetic and structural studies of heteroleptic platinum(II) and palladium(II) complexes containing thiacrown and monodentate phosphane ligands

Abstract

We wish to report the syntheses, spectroscopic, and structural properties for six new Pt(II) and Pd(II) heteroleptic complexes containing the monodentate phosphane ligands PTA (1,3,5-triaza-7-phosphaadamantane) or PMe3 (trimethylphosphane) and the crown trithioether [9]aneS3 (1,4,7-trithiacyclononane). All six reported complexes have the general formula [M([9]aneS3)(P2)](PF6)2 or [M([9]aneS3)(P)(Cl)](PF6) where M=Pt(II) or Pd(II) and P is the monodentate phosphane ligand. All six complexes form similar structures in which the metal center is surrounded by two sulfur atoms from the trithioether ligand and a cis arrangement of either the two phosphorus donors or the chlorido and phosphorus donor. The third sulfur from the [9]aneS3 interacts with the metal at a greater distance (2.711(2)Å–3.078(8)Å), resulting in elongated square pyramidal geometries. These axial distances are controlled by the donor abilities of the phosphane ligand with PTA and PMe3 serving as stronger donors. The two chlorido complexes show longer metal–sulfur interactions, consistent with the strong donor properties of the anionic chlorido ligand. Although the symmetrical bis complexes display typical 1H and 13C NMR behavior in the [9]aneS3 region, the less symmetrical chlorido complexes show a more complex pattern in their spectra. The 195Pt NMR chemical shifts are consistent with the presence of [S2P2+S1] or [S2PCl+S1] coordination environments.