Berchadsky Yves, Bernard-Henriet Christiane, Finet Jean-Pierre, Lauricella Robert, Marque Sylvain R A, Tordo Paul
Universités d'Aix-Marseille 1-3, CNRS--UMR 6517, Faculté des Sciences de St. Jérôme, case 542, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France.
Chemistry. 2006 Sep 18;12(27):7084-94. doi: 10.1002/chem.200600299.
Persistent noncyclic phosphoranyl radicals have been prepared and observed by electron paramagnetic resonance (EPR) for the first time. They were obtained by UV-photolysis of a solution containing a bis(trialkylsilyl) peroxide (R = Me, Et) and a tris(trialkylsilyl) phosphite (R = Me, Et, iPr). EPR parameters (a(P) approximately 100 mT) are typical of phosphoranyl radicals exhibiting a trigonal-bipyramidal structure, with the odd electron in an equatorial site. Analysis of the pseudo-first-order decay shows that these phosphoranyl radicals decay by S(H)2 homolytic substitution on the bis(trialkylsilyl) peroxide and by loss of a trialkylsilyloxyl radical (alpha-scission reaction). Both the S(H)2 and alpha-scission reactions depend on the steric bulk of the alkyl groups, that is, the bulkier the alkyl group, the slower the S(H)2 and alpha-scission reactions.
持久性非环状磷酰基自由基首次通过电子顺磁共振（EPR）制备并观测到。它们是通过对含有双（三烷基硅基）过氧化物（R = 甲基、乙基）和亚磷酸三（三烷基硅基）酯（R = 甲基、乙基、异丙基）的溶液进行紫外光解得到的。EPR参数（a(P)约为100 mT）是具有三角双锥结构的磷酰基自由基的典型特征，单电子位于赤道位置。对假一级衰变的分析表明，这些磷酰基自由基通过对双（三烷基硅基）过氧化物进行S(H)2均裂取代以及通过失去三烷基硅氧基自由基（α-断裂反应）而衰变。S(H)2和α-断裂反应均取决于烷基的空间位阻，即烷基越庞大，S(H)2和α-断裂反应就越慢。
