DINUCLEAR COMPLEXES OF PLATINUM WITH THE 4,4'-DIPYRAZOLYLMETHANE LIGAND - SYNTHESIS, CHARACTERIZATION, AND X-RAY CRYSTAL-STRUCTURE OF GAMMA-BIS(4,4'-DIPYRAZOLYLMETHANE-N,N')BIS[DICHLOROPLATINUM(II)]-N,N-DIMETHYLFORMAMIDE (1/2) AND RELATED COMPLEXES

The preparation and characterization of novel platinum complexes with the 4,4'-dipyrazolylmethane (dpzm) ligand is described. Some proposed conformational isomers of the square-planar, dinuclear platinum(II) complexes alpha-[Cl2Pt(mu-dpzm)2PtCl2].0.5dmf, beta-[Cl2Pt(mu-dpzm)2PtCl2], and gamma-[Cl2Pt(dpzm)2PtCl2].2dmf and the corresponding octahedral platinum(IV) complexes alpha-[Cl4Pt(mu-dpzm)2PtCl4].0.5H2O and beta-[Cl4Pt(mu-dpzm)2PtCl4].0.5dmf.0.5H2O have been synthesized and characterized. Interconversion of the conformational forms for each oxidation state can be accomplished by various means. The mononuclear complexes cis-[PtCl2(dmf)(dpzmH)]Cl and cis-[PtCl4(dmf)(dpzmH)]Cl.0.5dmf and dinuclear mixed-oxidation state complex [Cl4Pt(mu-dpzm)2PtCl2] were also prepared and characterized. The X-ray crystal structure determination of gamma-[Cl2Pt(dpzm)2PtCl2].2dmf is reported. The complex exists as discrete molecular units with strong hydrogen-bonding to dmf solvent molecules. Each platinum atom is coordinated to two bridging dpzm ligands in a cis geometry. The crystals are monoclinic, space group P2(1)/n, with cell parameters a = 9.790 (1) angstrom, b = 13.444 (2) angstrom, c = 12.174 (2) angstrom, beta = 105.74 (1)-degrees, and Z = 2. The structure was solved by the heavy-atom method and refined to R = 0.036 based on 2816 reflections.