Anodic Electrochemistry of Multiferrocenyl Phosphine and Phosphine Chalcogenide Complexes in Weakly Nucleophilic Electrolytes

Abstract

The anodic electrochemistry of several compounds containing two or three ferrocenyl moieties linked by a phosphine or phosphine chalcogenide group has been studied in dichloromethane containing [NBu 4 ][TFAB], where TFAB is the tetrakis(perfluoroaryl)borate anion, [B(C 6 F 5 ) 4 ] -. In two cases, namely [CpFe(C 5 H 4 )] 3 P (3) and [CpFe(C 5 H 4 )] 2 PdO(Ph) ( 6), the first one-electron-oxidation product is stable on the cyclic voltammetric (CV) time scale and subsequent oxidations at more positive potentials are also observed. The oxidations of [CpFe(C 5 H 4 )] 2 PPh (2) and [CpFe(C 5 H 4 )] 3 PdSe (7) are not reversible, and their monocations undergo follow-up reactions that are first-order and second-order, respectively, in the neutral compound. The results are consistent with a model in which the initial oxidation always involves a largely ferrocenyl-based HOMO which, nevertheless, has significant phosphine or phosphine chalcogenide character, allowing radical-type reactions, including dimerizations, at the linking group. The traditional nonaqueous supporting electrolyte anions such as [PF 6 ]and [BF 4 ]are shown to be responsible for many of the earlier difficulties in interpreting the anodic electrochemistry of this oft-studied class of compounds.

Electron‐Transfer Studies of trans‐Platinum Bis(acetylide) Complexes

“…In the cyclic voltammograms of 3b and 3c, irreversible redox processes are observed and are caused by intramolecular electron-transfer processes between the ferrocenyl groups and the phosphorus atom, including follow up reactions. [63,64] This behavior was also found for 3d by Geiger, Barrière, and Kirss [65] and is well studied for 1,1Ј-bis(diphenylphosphanyl)ferrocene [66,67] and diphenylphosphinoferrocene. [65] .…”

“…[63,64] This behavior was also found for 3d by Geiger, Barrière, and Kirss [65] and is well studied for 1,1Ј-bis(diphenylphosphanyl)ferrocene [66,67] and diphenylphosphinoferrocene. [65] . For tri-n-butylphosphine (3a), solely phosphorus oxidation is observed, owing to the lack of additional redox-active terminal groups.…”

“…[68] Electrochemical studies on phosphine selenides demonstrated that side reactions occur, including electron transfer from the selenium atom to the P III atom and Se-Se couplings; these reactions complicate the appro- priate studies. [65] In contrast, oxides and sulfides inhibit this undesired intramolecular electron transfer. On the basis of this observation, phosphines 3b-3d were treated with sulfur.…”

Oxidative Electrochemical Switching in Dithienylcyclopentenes, Part 1: Effect of Electronic Perturbation on the Efficiency and Direction of Molecular Switching

“…[25] The solvent dependence of the electronic and redox chemistry of 1 H was examined in detail to explore the role solvent and other environmental factors play in determining the chemical processes which the oxidised open and closed states undergo. The influence of solvent on the absorption spectra of 1 Ho and 1 Hc, although modest, is apparent (see Supporting Information, Figure S2).…”

Pentabenzylcyclopentadienyl molybdenum and tungsten hydrides: Syntheses, structures and electrochemistry of [MHCpBz(CO)2(L)] (L=CO, PMe3, PPh3)

“…However, the irreversibility of wave II implies that a homogeneous chemical process involving this species must take place before reduction. The first hypothesis that was considered to justify this behavior was the reaction between the [MoCp Bz (CO) 2 (PMe 3 )(CH 3 CN)] 2+ and the electrolyte anion PF À 6 [63,64]. It is well documented that BF À 4 may coordinate to molybdenum leading to the formation of zwitterionic complexes [MoCp 0 (CO) 3 (FBF 3 )] (Cp 0 = C 5 H 5 , Cp * , Cp Bz ) [18] and it has also been reported that fluorine abstraction from PF À 6 may be forced by highly acidic metal centers [65][66][67].…”