Nearly Linear Rh(I) Aggregates. Chemical and Spectroscopic Behavior of 2>3+ and Its Oxidation Products

Article abstract of DOI:10.1021/ja00228a021

The reaction of ⁺ (2) (dpmp is bis(diphenylphosphinomethyl)phenylphosphine) with excess methyl isocyanide yields green ³⁺: λ_max (absorption) 670 nm, λ_max (emission) 815 nm (in dichloromethane at 25 deg C).Green 2>3*1.3CH2Cl2 crystallizes from dichloromethane/ethyl ether in the triclinic space group P1 with a = 14.111(4) Angstroem, b = 16.654(5) Angstroem, c = 21.644(6) Angstroem, α = 91.42(2) degree, β = 102.43(2) degree, γ = 103.71(2) degree at 130 K.Least-squares refinement of 826 parameters with 8971 reflections yielded R = 0.095 and R_w = 0.107.The structure of the cation consists of three nearly planar RhP2(CNCH3)2 units connected through the dpmp bridge with Rh-Rh separations of 3.090(1) and 3.106(1) Angstroem.Addition of halogens or carbon tetrahalides to 2 produces two-fragment, three-center oxidative additions to form ³⁺ (X = I, Br, Cl), which have been isolated as the hexafluorophosphate salts and spectroscopically characterized.Electrochemical oxidation of 2 shows two one-electron oxidations.The oxidation products, ⁴⁺ and ⁵⁺, have been characterized by electronic and ESR spectroscopy and by chemical reactivity.The nature of the Rh-Rh interactions and the chemical behavior of these trinuclear species are explained by a simple molecular orbital picture involving the out-of-plane filled d_z2 and empty p_z orbitals.