Raw data from "Termination of carbomethoxyethyl radicals generated by Br-atom abstraction from MeCH(Br)COOMe with metalloradicals: implications for polyacrylate radical termination".

Acrylate radical termination is still controversial, with propositions spanning from 100% combination (Comb) to 100% disproportionation (Disp). This contribution analyzes the termination of CH3CH•(COOCH3) (RH•), generated by bromine abstraction from methyl 2-bromopropionate (MBP) by metalloradicals ([(CO)5Mn•], Me2E• (E = Si, Ge, Sn), nBu3Sn•, Ph3Pb•, Ph2Sb•). The Disp/Comb ratio strongly depends on the metalloradical nature (from 100:0 for Si2Me6 to 37.5:62.5±3.2 for Pb2Ph6). Control experiments and comparative terminations of (CH3)2C•(COOCH3) (RMe•), supported by DFT calculations, lead to a coherent mechanistic interpretation. Bimolecular termination of diffused RH• predominantly leads to Comb, while competing interception by a second metalloradical leads to 100% Disp via hydrogen-atom transfer (HAT) in a {RH•,metalloradical} caged pair, yielding a hydride intermediate ([(CO)5Mn-H], Me2E-H (E = Si, Ge, Sn), nBu3Sn-H, Ph3Pb-H, or Ph2Sb-H). An additional pathway, involving HAT within the caged {Me3E•,•EMe3} to yield Me3E-H and Me2E=CH2 intermediates, also contributes when E = Si and Ge. Selective generation of the {RH•,metalloradical} caged pair by photolytic activation of PhTe-RH or by the single-electron transfer (SET) reaction of MBP with NaPbPh3 leads to 100% Disp via the HAT process.