Organometallic redox systems

Casado C, Gonzalez B, Cuadrado I, Alonso B, Moran M, Losada J (2000) Mixed ferrocene-cobaltocenium dendrimers the most stable organometallic redox systems combined in a dendritic molecule. Angew Chem Int Ed 39 2135-2138... 

The photogalvanic effects are initiated by a homogeneous photoredox reaction of an electrolyte redox system with a suitable photoexcited organic or organometallic substance (dye), S. The photon absorption produces a short-lived, electronically excited dye molecule, S ... 

Electron donor-acceptor complexes, electron transfer in the thermal and photochemical activation of, in organic and organometallic reactions, 29, 185 Electron spin resonance, identification of organic free radicals, 1, 284 Electron spin resonance, studies of short-lived organic radicals, 5, 23 Electron storage and transfer in organic redox systems with multiple electrophores, 28, 1... 

Without doubt, the most noteworthy aspect of the redox behavior of the synthesized organometallic dendritic macromolecules 1-6, having a predetermined number of noninteracting ferrocenyl redox centers, is their ability to modify electrode surfaces. In this way, for the first time, electrode surfaces have been successfully modified with films of dendrimers containing reversible four- and eight-electron redox systems, resulting in detectable electroactive materials persistently attached to the electrode surfaces. ... 

Owing to the extremely large variety of solvents used in organic or organometallic chemistry, it is unlikely that all the pertinent electrochemical data can be found for a particular system and a particular solvent [30]. Thus the problem of the transposition of data obtained for one solvent to another frequently arises. As discussed for Ip or Aff, this should not be done without extreme precautions. Indeed, by substruction of the two equations, akin to Eq. (25), pertinent to each solvent, one obtains readily for a given O/R redox system... 

It is usually difficult to determine or impose activities, since activation coefficients are nearly always unknown for the redox systems investigated in organic or organometallic chemistry. Thus formal reduction potentials E° are measured, when feasible, rather than... 

This is a reaction with high atom economy and without the use of organometallic reagents, additives, or redox systems. Such an acetoxypalladation-initiated carbon-heteroatom multiple bond insertion-protonolysis system may extend the scope of transition metal-catalysed reactions pertaining to the insertion of carbon-heteroatom multiple bonds into metal-carbon bonds, and provide a new methodology in organic synthesis. The generality of the present catalytic system is shown in Table 10.2.[3]... 

Strehlow and coworkers studied various organometallic complexes. They formulated requirements for suitable reference redox systems [12] (1) The ions or molecules forming the reference redox system should preferably be spherical with as... 

To compare redox potentials of aqueous and nonaqueous systems, a variety of internal references were investigated. In 1984, Gritzner and Kuta recommended two systems for nonaqueous electrolytes that are also accepted by lUPAC [244]. The solvent-independent organometallic redox couples are fer-rocene/ferrocenium (Fc/Fc+) (E = 0.158 V vs saturated calomel electrode (SCE)) and bis(biphenyl)chromium(0)/(l) (BCr/BCr+) (E = —0.82 V vs SGE) [245]. Very stable electrode redox potentials Ei/i vs Ag/Ag+-cryptand electrode of 0.478 V for Fc/Fc+ and —0.616 V for BCr/BCr+ in EMIm tetrafluoroborate were measured [246]. 

The establishment of a solvent-independent reference electrode for the comparison of redox potentials in nonaqueous systems has a long story. It began with the concept of RblRb+ or Rb(Hg)IRb, followed by the proposal of using organometallic redox couples [2], In order to limit the number of redox systems used and then make the comparison easier, lUPAC recommended that the systems ferrocenelferrocenium, Fc° , and bis(biphenyl)chromium(0)lbis(biphenyl)chromium(l), BCi , need to be used as internal reference redox systems in nonaqueous media [2], These two complexes were selected arbitrarily from several published redox systems [2],... 

A60. J. P. Candlin, K. A. Taylor, and D. T. Thompson, "Reactions of Transition-Metal Complexes. Elsevier, Amsterdam, 1968. A review of types of reactions of metal complexes (e.g., substitution, combination, redox) reactions with various reagents (e.g., hydrocarbons, halides, carbon monoxide, and isonitrile) and preparation of new stabilised organic systems (e.g., metallocenes, carbenes). Intended for research workers, consequently written at a fairly high level, with emphasis on organometallics. A61. H. J. Keller, NMR-Untersuchungen an Komplexverbindungen. Springer, Berlin, 1970. Expansion of review article 37.1. 

---