Reduction–oxidation properties of organotransition-metal complexes. Part 2. The one-electron oxidation of tetracarbonyl(η-cyclopenta-dienyl) vanadium derivatives

Abstract

Cyclic-voltammetric studies in CH₂Cl₂ and MeCN have shown that [V(η-C₅H₅)(CO)₃L]{1; L = PPh₃, PMePh₂, PEt₃, P(NMe₂)₃, P[(OCH₂)₃CMe], and P(OPh)₃} and [V(η-C₅H₅)(CO)₂(dppe)](2; dppe = Ph₂PCH₂CH₃PPh₂) are oxidised at a platinum electrode to [V(η-C₅H₅)(CO)₃L]⁺(3) and [V(η-C₅H₅)(CO)₂(dppe)]+(4) respectively. For L = PPh₃,PMePh₂,PEt₃,and P(NMe₂)₃, andfor(2), this processis reversible, but for L = P(OPh)₃ or P[(OCH₂)₂-CMe] it is irreversible at all the scan rates used. Complexes (3; L = PPh₃ or PMePh₂) and (4) may be generated in CH₂CL₂ by treating (1) or (2) with [p-FC₆H₄N₂][BF₄]. and may be isolated, as their [PF₆]^– salts, by treating (1; L = PPh₃) or (2) with [NO][PF₆] in mixtures of methanol and toluene. The e.s.r. spectra of the paramagnetic cations are reported.