Synthesis and Redox Behavior of Chalconido Clusters of Nickel, Palladium, and Platinum

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Nine [M_3E_2(diphos)_3]^<2+> (M=Ni, Pd, Pt, E=S, Se, Te, diphos=1,2-bis(diphenylphosphino) ethane (dppe)) and six [M_3Se_2(diphos)_3]^<2+> (M=Ni, Pd, Pt, diphos=1,3-bis(diphenylphosphino)propane (dppp) or 1,4-bis(diphenylphosphino)butane (dppb)) clusters have been synthesized and X-ray structures of [Pt_3E_2(dppe)_3][BPh_4]_2 (E=Se, Te) were determined. The structures comprise three square-planar PtE_2P_2 coordination planes sharing two mu_3-E ligands. Cyclic voltammograms (CV) (20ﾟC or -18ﾟC) of [M_3E_2(dppe)_3]^<2+> (M=Ni, E=S, Se, Te) give two reversible couples which are one-electron process. CV's (20ﾟC or -18ﾟC) of [M_3E_2(dppe)_3]^<2+>one-electron process. CV's (20ﾟC OR -18ﾟC) of [M_3E_2(dppe)_3]^<2+> (M=Pd, Pt, E=S, Se, Te) except for (M=Pt, E=S) show one reversible couple which involves two-electron transfer. The ease of reduction follows the order Te>Se>S in these clusters [M_3E_2(dppe)_3]^<2+> (M=Ni, Pd, Pt).The CV's of [M_3Se_2(dppe)_3]^<2+> (M=Ni, Pd, Pt) containing 5-membered chelate rings give reversible couples and that of [M_3Se_2(dppp)_3]^<2+> (M=Ni) (6-membered chelate ring) gives reversible couples, but those of [M_3Se_2(dppp)_3]^<2+> (M=Pd, Pt) are irreversible. The CV's of [M_3Se_2(dppp)_3]^<2+> (M=Ni, Pd, Pt) (7-membered chelate ring) are all irreversible. Reduction potentials of [M_3Se_2(dppb)_3]^<2+> (M=Ni, Pd, Pt) having 7-membered chelate rings are the highest and accordingly these are the easiest to reduce.