Persilylated phosphoranyl radicals: the first persistent noncyclic phosphoranyl radicals.
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.
Berchadsky
Yves
Y
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.
Bernard-Henriet
Christiane
C
Finet
Jean-Pierre
JP
Lauricella
Robert
R
Marque
Sylvain R A
SR
Tordo
Paul
P