Noncomplementary oxidation-reduction

Noncomplementary reactions, as shown in equation 1.26, involve unequal numbers of oxidants and reductants because the number of electrons gained or lost by each metal differs.6 Noncomplementary reactions, especially for large biomolecules, must proceed by a number of bimolecular steps because the possibility of termolecular or higher-order collisions is very small. 

Reductants with the next stable oxidation state two units higher are formally two-electron reductants e.g., Sn(ll), T1(I) and Pt(II). Reactions of Pt(II) usually are with Pt(lV) complexes and as a result have the stoichiometry of substitution processes (the reduction of Au(lII) by Pt(Il) occurs]. The major problem in assessing reactivity patterns in these reactions is the variety of rate laws and paucity of data. Because noncomplementary reactions produce unstable oxidation states that react by a variety of mechanisms, rate laws are often not comparable reactivity patterns are highly dependent on the oxidant in ways that are not yet analyzable. 

Multiple-oxidation-state reagents are ideal for catalysis of noncomplementary reactions, e.g., in the Sn reduction of Fe catalyzed by the [Taj CluJ cluster which proceeds by the mechanism ... 

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