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 .