Systematic synthesis of mixed-metal clusters via capping reactions. Characterization of a set of octanuclear carbido clusters involving rhenium and various platinum metals

Article abstract of DOI:10.1021/om00092a031

The cluster [Re₇C(CO)₂₁]^3- reacts with a variety of platinum metal based electrophiles to afford the new mixed-metal clusters [Re₇C(CO)₂₁ML_n]^2-, where ML_n = Rh(CO)₂, Rh(CO)(PPh₃), Rh(COD), Ir(COD), Pd(C₃H₅), Pt(C₄H₇), and Pt(CH₃)₃. These complexes have been isolated as salts with various large cations and have been characterized by IR (ν_CO), ¹H NMR, and fast atom bombardment mass spectroscopies. Variable-temperature ¹³C NMR spectroscopic studies of selected complexes show that each of these compounds adopts a 1,4-bicapped octahedral geometry in solution. This observation is in accord with the solid-state structure of [PPN]₂[Re₇C(CO)₂₁Pt(C₄H ₇)], which has been determined by X-ray crystallography. The compound crystallizes in the monoclinic space group P2₁/n, with a = 13.412 (5) A?, b = 18.095 (6) A?, c = 20.686 (3) A?, and β = 107.21 (2)°, Z = 2, and the structure has been refined to R(F) = 0.0618 and R(wF) = 0.0688. Cyclic voltammetry studies reveal two oxidation waves for each compound, with E_1/2 strongly dependent on ML_n.