Redox Isomeric Ferrocenyl Styrylruthenium Radical Cations with Diphenyl-Substituted β-Ketoenolato Ligands

Abstract

We report on 18-valence-electron ferrocenyl vinylr u t h e n i u m co n j u g a t es 4The complexes undergo two reversible one-electron oxidations whose potentials depend on the aryl substituents R. The one-electron oxidized forms of these complexes exist as two different isomers, which differ with respect to whether the electron loss has primarily occurred from the ferrocene or the styrylruthenium site. These isomers are clearly distinguished by characteristic features in their infrared, near-infrared, EPR, and Moßbauer spectra. Electron-withdrawing substituents R at the Ph R 2 acac coligand increase the proportion of the ferrocenium-type species, whereas electrondonating ones have the opposite effect.

Tailoring Valence Tautomerism by Using Redox Potentials: Studies on Ferrocene‐Based Triarylmethylium Dyes with Electron‐Poor Fluorenylium and Thioxanthylium Acceptors

“…The shown complex with an acetylacetonate (acac) and related β-ketoenolato complexes with 4-substituted phenyl groups instead of Me exist as two distinguishable valence tautomers. [24] When the acac coligand is however replaced by its bis-CF 3 derivative hfac or by the simple chloro ligand, only the isomer with an oxidized ferrocenium centre is present. Removing the phenylene spacer finally leads to an asymmetric mixed-valent description.…”

Ferrocenyl-Substituted Triazatruxenes: Synthesis, Electronic Properties, and the Impact of Ferrocenyl Residues on Directional On-Surface Switching on Ag(111)

“…Discrepancies between a ferrocene-centered oxidation and a delocalized HOMO have already been noted for other ferrocenes with a π-extended substituent or another redox-active constituent attached. 90 , 91 They are ascribed to the extra stabilization of a ferrocenium ion imposed by a sizable lowering of the Fe d z 2 orbital during ferrocene oxidation. We note that the same effect also underlies the inverted energy ordering of the frontier MOs in ferrocene as well as phenylferrocene and their corresponding ferrocenium ions (i.e., d x 2 – y 2 , d xy < d z 2 in ferrocene, but d z 2 < d x 2 – y 2 , d xy in the ferrocenium ion).…”