1‘-(Diphenylphosphino)ferrocenecarboxylic Acid and Its P-Oxide and Methyl Ester:  Synthesis, Characterization, Crystal Structure, and Electrochemistry

Abstract

The ferrocene derivative (η5-C5H4PPh2)Fe(η5-C5H4COOH) (3), a potential hybrid phosphine ligand with heteroannular soft and hard donor groups, was synthesized in 71% yield from 1-phenyl-1-phospha[1]ferrocenophane by ring opening with phenyllithium, followed by reaction with carbon dioxide and acidification. Oxidation of 3 with hydrogen peroxide and its esterification with diazomethane provided the derivatives, phosphine oxide 4 and methyl ester 5, respectively. The new compounds were characterized by IR, UV/vis, MS, and NMR spectroscopy, the degenerate 1H NMR spectra being assigned with the aid of selective 1H{1H} decoupling, 1H,1H-COSY, 13C HMQC, and n J(P,C) from APT. The solid-state structures of 3−5 were determined by single-crystal X-ray diffraction. Voltammetric measurements of 3−5 and related monosubstituted derivatives in acetonitrile revealed that the phosphines are first oxidized to the corresponding ferrocenium derivatives which are then the subject of the intramolecular electron transfer from the phosphine group to iron, the resulting species being immediately stabilized by further electrochemical and/or chemical oxidation to give phosphine oxides. The second independent electrochemical process is the reversible oxidation of these ferrocene/phosphine oxides to ferrocenium/phosphine oxides. There are further electrochemical processes associated with the irreversible oxidation of the carboxyl group.

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] .…”

The Chemistry of Phosphanyl‐ferrocenecarboxylic Ligands

“…[20] A synthesis of Hdpf by stepwise metalation/functionalization of 1,1Ј-dibromoferrocene has been reported by Butler et al [22] In addition to the standard characterization, Hdpf and some related compounds were studied in detail by mass spectrometry [23] and by electrochemical methods. [17] In cyclic voltammograms in acetonitrile, Hdpf shows the expected one-electron oxidation to the corresponding ferricenium at E°Ј = +0.32 V vs. ferrocene/ferricenium reference, the shift to higher potential vs. the reference couple being in agreement with the electron-withdrawing nature of both substituents at the ferrocene unit (process A in Scheme 4). However, this electrochemical oxidation is followed by chemical complications, resulting in a pseudoreversible behaviour upon back-scan.…”

“…In the original synthesis of Hdpf (Scheme 3) [17] we made use of the ring opening in the strained ferrocenophane 6 [18] with phenyllithium to give 1Ј-(diphenylphosphanyl)lithioferrocene (7). [18b,19] In situ carboxylation of 7 with excess solid carbon dioxide and a subsequent acidification of the water-soluble part of the reaction mixture followed by recrystallization of the crude product afforded analytically pure Hdpf as an air-stable, rusty red-brown crystalline solid in typical yields around 80 %.…”

2,3,4,7-Tetrahydro-1H-inden-2-ol: synthesis, molecular structure and coordination chemistry

“…2,3,4, 1 was synthesised by sodium reduction of indan-2-ol in liquid ammonia by analogy to published methods [11]. Crystals suitable for X-ray analysis were obtained by slow evaporation of a dichloromethane solution of 1.…”

“…A wide variety of methods for the synthesis of ferrocenoyl ester derivatives are found in the literature, among them reaction of FeCl 2 with cyclopentadienyl ester derivatives [1], condensation of chlorocarbonylferrocene with hydroxo derivatives [2], oxazoline ringopening reaction of ferrocenoyloxazole derivatives [3], reaction of ferrocene carboxylic acid with diazomethane [4], reaction of ferrocenoyl imidazolide with hydroxo derivatives [5], haloferrocene with acids [6], reaction of ferrocene carboxylic acid with hydroxo derivatives [7], and reaction of 2-(N,N-dimethylaminoethylferrocene)carboxylic acid with sodium bicarbonate and methyl iodide [8].…”