Catalyzed Radical Termination in the Presence of Tellanyl Radicals

• Published in: Chemistry : a European journal 2017-10, Vol.23 (56), p.13879-13882
• Main Authors: Ribelli, Thomas G., Rahaman, S. M. Wahidur, Matyjaszewski, Krzysztof, Poli, Rinaldo
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical Sciences; Chemistry; Coordination chemistry; Decomposition; density functional calculations; Disproportionation; Photochemicals; Polyethylene glycol; Polymers; radical termination; radicals; V-601; Viscosity
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201703064

The decomposition of the diazo initiator dimethyl 2,2′‐azobis(isobutyrate) (V‐601), generating the Me2C.(CO2Me) radical, affords essentially the same fraction of disproportionation and combination in media with a large range of viscosity (C6D6, [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 Me2C(TeMe)(CO2Me) 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 Te2Ph2. The bimolecular termination of (CH3)2C.CO2CH3 radicals generated from V‐601 is essentially solvent‐ and temperature independent, contrary to that of the same radicals generated from (CH3)2C(TeMe)CO2CH3; DFT calculations and V‐601 photolysis in the presence of Te2Ph2 suggest an unprecedented Te‐catalyzed disproportionation to account for these different results (see figure).