One-electron oxidation of selenium and tellurium compounds

One-electron oxidation of organoselenium and organotellurium compounds results in initial formation of a radical cation (equations (19) and (20)). The eventual fate of the radical cation depends on several variables, but is typically a Se(lV) or Te(lV) compound. The scope of this section will be the one-electron oxidation of selenides and tellurides that are not contained in a heteroaromatic compound, and ones in which the Se and Te are bonded to two carbons, rather than to other heteroatoms. Tellurium- and selenium-containing electron donor molecules have been reviewed. 

In several cases, a series of compounds containing the chalcogens O, S, Se, and Te has been prepared, and the behavior of the compounds under oxidizing conditions evaluated and compared. In other cases, a more limited set of compounds has been evaluated in the same way. In another subset, the impact of substituents has been examined. Finally, the impact of other structural variables, such as the hybridization of the atoms and the structure of the groups to which the chalcogen is attached, have been explored. 

To make clear what type of oxidation potential data are being cited, when thermodynamics-based pulse radiolysis data are cited, such data will be labeled E°, while Eh2 will be used for reversible CV data. IPs are obtained under adiabatic conditions, with no gain or loss of heat. 

Simply using the electronegativities or IPs of the chalcogens would lead to the prediction that for a series of compounds, the O-containing compound would oxidize least readily and the Te-containing compound would be most easily oxidized (Table 7). In most cases, the oxidation data match this prediction. Only in a small number of cases does it not, and in those cases it can be attributed to the structural environment in which the chalcogen is found. 

The oxidation potentials of diphenyl selenides ° and diphenyl tellurides have been measured by electrochemical methods, as well as by pulse radiolysis. Pulse electrolysis was used to determine E° values for diphenylsulfide (84), diphenylselenide (85), and diphenyltelluride (23). In each case, equilibrium 

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