17-Electron alkynyl complexes of cyclopentadienyliron(III)

Abstract

The complexes [Fe(CCR)(L–L)(η-C₅R′₅)][R = Bu^t, CO₂Me, CO₂Et, SiMe₃, Ph or CH₂OMe, L–L = Ph₂PCH₂PPh₂(dppm), R′= H; R = Bu^t or Ph, L–L = Ph₂PCH₂CH₂PPh₂(dppe), R′= Me] undergo reversible one-electron oxidation at a platinum electrode in CH₂Cl₂. Chemical oxidation with [Fe(η-C₅H₅)₂][PF₆] gave the isolable salts [Fe(CCR)(dppe)(η-C₅Me₅)][PF₆](R = Bu^t or Ph) which Mössbauer spectroscopy suggests to be complexes of Fe^III. The ESR spectra of these salts, and of the cations [Fe(CCR)(dppm)(η-C₅H₅)]⁺(R = Bu^t, CO₂Me, CO₂Et or Ph), generated by in situ oxidation with [Fe(η-C₅H₅)₂][PF₆], are similar to those of low-spin d⁵ complexes of Cr^I, Mn^II and Fe^III.