Reduction–oxidation properties of organotransition-metal complexes. Part 17. The reaction of [Rh(CO)(PPh3)(η-C5H5)] with one-electron oxidants: fulvalene complex and silver adduct formation, and the X-ray crystal structure of [Ag{Rh(CO)(PPh3)(η-C5H5)}2][PF6]·C6H5Me

Abstract

Cyclic voltammetry shows that [Rh(CO)(PPh3)(η-C5H5)](1) undergoes irreversible one-electron oxidation to the reactive radical cation [Rh(CO)(PPh3)(η-C5H5)]+(2); chemical oxidation of (1), with [Fe(η-C5H5)2][PF6] or [N2C6H4F-p][PF6], or controlled potential electrolysis gives the fulvalene complex [Rh2(CO)2(PPh3)2(η5:η′5-C10H8)]2+(3). Cyclic voltammetry shows that (3) undergoes a reversible two-electron reduction, and sodium amalgam or bulk electrolysis affords the complex [Rh2(CO)2(PPh3)2(η5:η′5-C10H8)](4). The reaction of (1) with AgPF6 in toluene gives the adduct [Ag{Rh(CO)(PPh3)(η-C5H5)}2][PF6]·C6H5Me (5), X-ray structural studies on which reveal a near linear Rh–Ag–Rh framework. Complex (5) acts as a stabilised source of (2), reacting with NO gas to give [Rh(PPh3)(NO)(η-C5H5)][PF6], [Rh(CO)(PPh3)(η-C5H5)], and silver metal.