Electron Transfer from Tetrakis(isocyanide)rhodium(I) Monomers, and the Oligomers to Iron(III) and Cobalt(III) Complexes. Enhancement of the Reactivity by the Oligomerization

Article abstract of DOI:10.1246/bcsj.55.3482

Electron transfer reactions from tetrakis(isocyanid)rhodium(I) (⁺ to iron(III) complexes of the ³⁺ type (N-N = 1,10-phenanthroline, 2,2'-bipyridine) proceed through precursor complexes formed between ⁺ and ³⁺ with 1:1, 1:2, and 2:1 stoichiometry..A similar scheme is suggested for the reaction of bis(isocyanide)bis(triphenylphosphine)rhodium(I) with the same oxidants.The intramolecular electron transfer rate constants k₁ in the 1:1 precursor complexes have been determined in MeCN at 298 K.In accordance with Marcus theory, the log k₁ values are linearly related with the reduction potentials of oxidants with the theoretical slope of 8.5.The ⁺ cations form oligomers in MeCN; +>n (n = 2,3), and the equilibrium constants for oligomerization have been determined.For a given oxidant ³⁺ (bpy = 2,2'-bipyridine), the log k₁ value of +>n increases in parallel with the HOMO energy of +>n; monomer less than dimer less than trimer.