Electron transfer general reactivity patterns

Because the breadth of chemical behavior can be bewildering in its complexity, chemists search for general ways to organize chemical reactivity patterns. Two familiar patterns are Br< )nsted acid-base (proton transfer) and oxidation-reduction (electron transfer) reactions. A related pattern of reactivity can be viewed as the donation of a pair of electrons to form a new bond. One example is the reaction between gaseous ammonia and trimethyl boron, in which the ammonia molecule uses its nonbonding pair of electrons to form a bond between nitrogen and boron ... 

Studies of the simple electron transfer properties of coordinated dioxygen are in a preliminary stage. The definition of reactivity patterns is obscured by inconsistencies and the lack of key pieces of information, as indicated by the comments above. Nevertheless, there is hope that some general features will emerge ... 

Temperature and pressure effects on rate constants for [Fe(phen)3] +/[Fe(phen)3] + electron transfer in water and in acetonitrile have yielded activation parameters AF was discussed in relation to possible nonadiabaticity and solvation contributions. Solvation effects on AF° for [Fe(diimine)3] " " " " half-cells, related diimine/cyanide ternary systems (diimine = phen, bipy), and also [Fe(CN)6] and Fe aq/Fe aq, have been assessed. Initial state-transition state analyses for base hydrolysis and for peroxodisulfate oxidation for [Fe(diimine)3] +, [Fe(tsb)2] ", [Fe(cage)] " " in DMSO-water mixtures suggest that base hydrolysis is generally controlled by hydroxide (de)hydration, but that in peroxodisulfate oxidation solvation changes for both reactants are significant in determining the overall reactivity pattern. ... 

The general patterns of the reactivity of aryllead triacetates could be explained by the occurrence of free radicals, generated by a single-electron-transfer mechanism or via a SrnI process. 

In all proton transfer reactions, the electron-rich base donates an electron pair to the acid, which usually has a polar H—A bond. Thus, the H of the acid bears a partial positive charge, making it electron deficient. This is the first example of a general pattern of reactivity. 

---