Electron-Transfer-Chain ETC Catalyzed Reactions

Each of these two areas can be further divided into two parts, depending on the nature of the redox change during the catalytic cycle electron transfer versus atom transfer. The latter mode of redox change is necessarily an inner-sphere version of the electron-transfer reaction, whereas the first mode is frequently of the outer-sphere type [8]. 

Chain inorganic reactions have been reviewed several times [9-14] whereas redox catalysis is an extremely large area dealing with metal-catalyzed oxidations [15, 16] (cf. Section 2.4) and bioorganic catalysis [17, 18] (cf. Section 3.2.1). Many important references concern electrochemistry (heterogeneous electron transfer) and therefore are not cited here but interested readers can find them in [4]. 

2 Electron-Transfer-Chain (ETC) Catalyzed Reactions 3.2.8.2.1 Principles 

Thermodynamically favorable reactions such as A------ B which suffer from ki- 

Catalysis is obtained because the rate of the chemical step is often considerably more favorable at the odd-electron level than at the even-electron (closed-shell) level. Indeed, most of the time inorganic radicals react about 10 times faster than their isostructural diamagnetic analogs. For organic radicals, the rate enhancement is even larger [9]. 

---

Redox reagents are useful for stoichiometric electron-transfer reactions, catalytic initiation of electron-transfer-chain (ETC) catalyzed reactions, as redox mediators (by outer-sphere electron transfer) or redox catalysts (by inner-sphere electron transfer) of redox reactions, as part of sensory devices when then are attached to... 

Electrocatalysis, also named Electron-Transfer-Chain (ETC) catalysis, whereby a reaction (mostly of non-redox type) is catalyzed by an electron (reduction) or by an electron hole (oxidation). Organotransition-metal complexes can carry an electron or an electron hole and, if they achieve this function without decomposition, they are electron-reservoir complexes [6],... 

Thus the first electron transfer to Pb relates to the reaction (a) in Section 7.4.3.1.1, and the second involves the oxidation of the cyclobutyl radicals either by electron transfer/deprotonation with Cu" in equation (17) or by ligand transfer of chlorine with PlAci in equation (18). When the product of a generic reaction is itself a radical cation (such as in Sections 7.4.3.1.8 and 7.4.3.1.9), an electron-transfer chain or ETC process can ensue, as in the hole-catalyzed cycloadditions and autoxidations of dienes,The electron-transfer propagation sequence for the latter is simply given as in equations (19) and (20). 

---