Propagation Mechanisms in Ring-Opening Polymerization of Small Phosphorus Heterocycles: Toward Free-Radical Polymerization of Phosphines?

摘要: The mechanism and kinetics of the propagation step in radical ring-opening polymerization methylphosphirane, -phosphetane, -phospholane, also phenylphosphetane, were studied via high-level ab initio calculations. It was found that should occur attack carbon-centered propagating at phosphorus center ring. This is a facile process (with reaction rates order 104−106 L mol-1 s-1 298.15 K), driven by creation transition structure resembles (relatively stable) stretched phosphoranyl radical. fastest for four-membered phosphetanes, reflecting best compromise between strain released partially broken ring bond. Though slightly slower, opening three-membered phosphirane occur, but five-membered phospholane not thermodynamically favorable. On basis calculations t...