Molybdenum complexes oxidation/reduction

Simple oxidation/reduction has also been studied for a wide range of isocyanide complexes. Again those complexes containing mainly molybdenum-carbon bonds have been reviewed in... 

For both complexes, reversible metal-centered one-electron oxidations and reductions have been observed. The products of such redox processes have been examined by monitoring the EPR and electronic spectra obtained by controlled-potential electrolysis and, in the case of the molybdenum complex, have been identified as [Mo(IV)0(TMTEC)]+ and [Mo(VI)0(TMTEC)] ions. 

With the similar molybdenum complex the yield of ammonia reaches only ca 0.7 mol per metal atom, the remainder being evolved as free dinitrogen, with molybdenum being oxidized to molybdenum(III). Apparently, however, no such complexes have been observed as intermediates in dinitrogen reduction in protic media. 

Redox processes are fairly common in the formation of Z —CO— complexes of transition metals, and an example is given in Eq. (9). In this reaction, titanium is oxidized from the + 2 to the +3 state, thus becoming a better Lewis acid, and the molybdenum dimer is reductively cleaved, thus developing Z —CO— donor character (59). A characteristic low-frequency Z —CO— band is observed in the IR spectrum, and a crystal structure is available. A proposed mechanism for the redox process, based on CO mediated electron transfer, is discussed in Section IV,C. 

The second method of establishing oxidation states employed redox titration using the redox dye dichlorophenolindophenol (DCIP) based on the knowledge that tetrahydropterins reduce DCIP instantaneously while qui-nonoid dihydropterins react slowly and 7,8-dihydropterins do not reduce DCIP at all. As previously mentioned in this chapter, DCIP oxidation of Moeo within several molybdoenzymes was determined to be a two-electron process, suggesting a dihydropterin reduction state that was speculated to be the quinonoid tautomer. The results of stoichiometric additions of DCIP to the molybdenum complexes of reduced pterins showed that no oxidation of... 

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