Electrochemistry of clusters: V. Study of binuclear complexes and trinuclear clusters with PdPd and PdPt bonds stabilized by Ph 2PCH 2PPh 2 ligands

Abstract

Electrochemical characteristics of ten complexes containing PdPd and PdPt bonds are reported. The syntheses of the new cationic clusters [{PdMCo(CO) 3(μ-dppm) 2X}(PF 6)], M = Pt, X = PPh 3; or M = Pd, X = PPhMe 2) are described. The electrochemical reuslts are solvent dependent. In 1,2-C 2H 4Cl 2 the bimetallic complexes bridged by two bis(diphenylphosphino)methane (dppm) ligands undergo an irreversible two-electron reduction and an irreversible one-electron oxidation. The reduction potentials mainly depend on the nature of the metalmetal bond, whereas the oxidation potentials are mostly influenced by the nature of the ligand. In DMSO, the tetranuclear [PD 2Co 2(CO) 7(μ-dppm) 2], the trinuclear [Pd 2CoI(CO) 3(μ-dppm) 2] and [{Pd 2Co(CO) 3(μ-dppm) 2PR 3}(PF 6] clusters undergo two quasi-reversible one-electron reduction steps, whereas the corresponding tetranuclear clster [PtPdCo 2(CO) 7(μ-dppm) 2], and the trinuclear clusters [PtPdCoI(CO) 3(μ-dppm) 2], and [{PtPdCo(CO) 3(μ-dppm) 2PR 3}(PF 6] undergo a single quasi-reversible two-electron reduction. All the oxidation steps of the clusters are irreversible, the first oxidation step is assigned to the fragment attached to the triangular core: [Co(CO) 4] − and I −, while further oxidation involves the cationic triangular cluster.