Should dithiophosphinate esters function as RAFT agents?

(Chemical Equation Presented) High-level ab initio calculations indicate that ^•CH₃ addition to the sulfur center of S=P(Z)(Z′)SCH₃ (Z,Z′ = CH₃, CN, OCH ₃, Ph) is considerably less exothermic than addition to the corresponding RAFT agents, S=C(Z)SCH₃. This suggests that dithiophosphinate esters may have only limited use in controlling free-radical polymerization, but should make excellent radical chain carriers in organic synthesis. The results cast doubt on the notion that phosphoranyl radicals are more "intrinsically" stabilized than carbon-centered radicals.