Mixed Ruthenium-rhodium Trinuclear Complex [Ru₂Rh(m₃-oo)(ai-CH₃COO)₆(L)3]⁺(L = H₂O or Pyridine)

The preparation and purification method of a new ruthenium(III)-rhodium(III) cluster, [Ru₂Rh(u₃-0)(u-CH₃COO)₆(L)₃]⁺(L = H₂0 or pyridine (py)), are described. The mixed-metal structure was confirmed by the¹H and¹³C NMR spectra (splitting of all the signals to a 1:2 intensity ratio) and the metal 3d electron signal intensities of the X-ray photoelectron spectra. The mixed-metal aqua and pyridine complexes exhibit an intense visible absorption peak at 576 nm (e 2000 M^-1cm^-1) and 590 (3980), respectively. Three reversible one-electron-redox waves are observed at +1.68, +0.79, and -0.78 V vs the Ag/Ag⁺electrode for the pyridine complex in CH₃CN and are assigned to [Ru₂Rh]^3+/2+, [Ru₂Rh]^2+/+, and [Ru₂Rh]^+/0, respectively. The^lH NMR spectrum of the aqua complex in CD₃OD changes slowly as the substitution of CD₃OD for the aqua ligands takes place, first-order rate constants being 6.0 X 10^-5(per Ru) and 1.2 X 10^-4s^-1at the ruthenium and the rhodium centers, respectively, at 21 °C.