Catalyzed Radical Termination in the Presence of Tellanyl Radicals

The decomposition of the diazo initiator dimethyl 2,2'-azobis(isobutyrate) (V-601), generating the Me₂ C^. (CO₂ Me) radical, affords essentially the same fraction of disproportionation and combination in media with a large range of viscosity (C₆ D₆ , [D₆ ]DMSO, and PEG 200) in the 25-100 °C range. This is in stark contrast to recent results by Yamago et al. on the same radical generated from Me₂ C(TeMe)(CO₂ Me) and on other X-TeR systems (X=polymer chain or unimer model; R=Me, Ph). The discrepancy is rationalized on the basis of an unprecedented RTe^. -catalyzed radical disproportionation, with support from DFT calculations and photochemicaL V-601 decomposition in the presence of Te₂ Ph₂ .