Ferrocenium salts

Vesicles can be formed not only by simply adding a surfactant (eventually with a cosurfactant) but also upon sonification. As shown by Gokel and coworkers [32], their reversible collapse can be controled chemically by influencing the polarity of head groups. For instance, cholestanyl ferrocenylmethyl ether 92 does not form any aggregates but its corresponding ferrocenium salt obtained by oxidation afforded vesicles upon sonification. However, the aggregates collapsed when ferrocenium ion was reduced to its normal... 

An interesting technique recently published uses FTIR spectroscopy to detect anions [149]. Thin films of tetraalkylated ferrocenium salts were evaporated onto ATR crystals. Exposure to anion-containing solutions caused incorporation of the anions, and they could then be detected via their IR absorbances. Limits of detection for 10-min analyses varied from 10 6 to 10 s M for a variety of anions however, this technique cannot be used to detect anions that do not have IR absorbances, such as halides. 

Kopf-Maier P, Kopf H, Neuse EW (1984) Ferrocenium salts- the first antineoplastic iron compounds. Angew Chem Int Ed Engl 23 456-457... 

Representative 57Fe Mossbauer Data for Ferrocenes and Ferrocenium Salts... 

A large number of cationic photoinitiators are known. The most significant from the commercial point of view are aryldiazonium, diaryliodon-ium, triarylsulfonium, and ferrocenium salts. These salts possess anions of very low nucleophilicity which do not terminate the polymerization process. Nonionic cationic photoinitiators such as organosilanes, latent sulfonic acids, and some other miscellaneous compounds are also used. 

Fe" Sandwich Complexes Ferrocenium Salts [FeCpiUX] and (FeCp (v -C6Me6)l[SbX6l2... 

Iron(III) trichloride is commercially available both as the anhydrous or hydrate form which can also be refluxed in thionyl chloride to generate the anhydrous form (purified by sublimation) most often used [209], Anhydrous iron trichloride is about as strong as ferrocenium salts, but it is not necessarily innocent. It is sometimes used to recover functionalized metal-free hydrocarbon derivatives which have been transformed by temporary complexation and activation on a transition-metal center [210]. 

The reaction of concentrated sulfuric acid with neat ferrocene is a method of preparation of ferrocenium salts ... 

Commercially available 1,2 and 1,4 quinones are easily handled. The formal potential of the 1,4-benzoquinone/hydroquinone couple at pH 0 is ca 0.30 V relative to FeCp2. A variety of ferrocene derivatives including l,l -diacetylferrocene have been oxidized by 1,4-benzoquinone in the presence of HBF4, and the ferrocenium salts have been prepared using this reaction [284]. 

Initiation by ferrocenium salts of an ETC-catalyzed chelation involving an endergonic cross propagation step... 

During the past twenty years, development of compounds that efficiently initiate polymerization on irradiation have made possible the development of several new commercially important technologies based on these photoinitiators [1]. Their use in UV curable coatings is particularly notable. The most useful photoinitiators that have been explored to date are radical photoinitiators. Many applications today use this technology, in spite of important drawbacks [2]. The recent development of diaryliodonium, triarylsulfonium and ferrocenium salts as highly efficient photoinitiators for cationic polymerization has generated a new class of fast polymerizations. 

On the basis of this analysis, we decided to develop new weakly coordinating anions that will be associated with various diaryliodonium salts, triarylsulfonium salts and ferrocenium salts... 

It has been briefly reported that the cluster in dichloromethane solution, undergoes first a reversible one-electron oxidation (E0 = + 0.3 V), followed by second an irreversible oxidation (Ep= +0.8V). As expected, chemical oxidation by ferrocenium salt afforded the monocation [PtRh2(p3-CO)2 (PPh3XCOXC5Mes)2]+, which has not been characterized by X-ray [67]. 

In the (keto)coumarin/amine/ferrocenium salt system, the ferrocenium salt plays a crucial role that is rather complex. In a three-component photoinitiator system [238,239] consisting of a coumarin, an iron arene complex such as CpFe +Ar and a phenylglycine derivative as an amine, the first step of the photoreaction occurs between the dye and the complex according to an electron process. The amine reacts with the radical (created on the complex) through hydrogen abstraction. Therefore, no detrimental ketyl radicals are formed. 

Finally, four-component systems are also available the complexity of the mechanisms involved increases. This is exemplified by the dye (Rose Bengal, eosin)/ ferrocenium salt/amine/hydroperoxide system [243,244]. The direct photolysis of the dyes and the salt in the presence of oxygen and hydroperoxide has been investigated. In a general way, the primary process is the interaction between the dye and the ferrocenium salt that results in an electron transfer. Then, the reactions of the radical (formed in situ on the ferrocenium salt) with the amine, oxygen, and hydroperoxide lead to radicals. Oxygen is thus eliminated. Dark reactions can... 

Iron Arene Complexes-Based Photoinitiators Iron arene complexes or ferrocenium salts are attractive photoinitiators for cationic polymerization of... 

Upon irradiation, ferrocenium salts lose their arene ligands leading to generation of iron-based Lewis acids that coordinate with epoxide monomers. One of the monomers undergoes ring opening followed by addition of a new monomer. Arene... 

T. Wang, et al., Several ferrocenium salts as efficient photoinitiators and thermal initiators for cationic epoxy polymerization. J. Photochem. Photobiol. A Chem. 2007, 187(2-3), 389-394. 

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