Radical Reactions in an X‐Irradiated Phosphaalkene: A single‐crystal ESR study

Abstract

(5.VII.93)Single crystals of 1-[2,4,6-tri(wrt -butyl)phenyl]-2-phenylphosphaetbene (PPPE) and of 'D-and "C-enriched PPPE were studied by ESR after X-ray irradiation. Two phosphorus-centered radicals were trapped in the crystals. The first one was characterized by its 3'P, 'H-, and '3C-hyperfine tensors, the second one exhibited coupling with "P only. Comparison of these parameters with those predicted by ub initio calculations on some phosphinyl species indicates that these two radicals probably result, on the one hand, from an addition of a H-atom to the C-atom of the P=C bond and, on the other, from a cyclization of the parent molecule. The proposed mechanisms are consistent with the mutual orientations of the hyperfine eigenvectors and bond directions in the undamaged molecule. A C-centered radical which results from an addition of a H-atom to the P-atom of the phosphaethylene bond is also detected.

Benzo[d]-1,2-oxaphospholes as Precursors of Stabilized C-Centered Radicals

“…On the other hand, the formation of C-centered radicals attached to a phosphorus atom has been previously described . The evidence is strongly against any significant C−P dπ−pπ bonding in the ground state of these radicals and agrees with spin-density essentially localized on the carbon atom.…”

Hindered Rotation around a C−•PH Bond: A Single-Crystal EPR Study of the Diphenyldibenzobarrelenephosphinyl Radical

“…We have already shown, , that the most stable geometry of a HP−CR 3 phosphinyl radical corresponds to the staggered configuration (HPCR dihedral angle = 180°). The salient feature of the spectra obtained with the phosphinyl radical R2 trapped in the crystal of 2 is that each “site” detected at room temperature seems to generate only two “configurational sites” at 77 K. This is in contrast with the situation observed with a crystal of D-1 where the P−D bond of the phosphinyl radical is blocked, at 77 K, with the same probability along the three orientations staggering the barrelene C 9 −C bonds.…”

Radical reactions in a single crystal of phosphaalkene: EPR and ab initio calculations of phosphoniumyl radical cations

“…In the case of diph~sphene~,~ it was shown that the P=P moiety rapidly reacts with radicals to produce phosphinyl radicals (RzP) and more recently we could demonstrate, from solid-state EPR studies, that this mechanism occurs as well for the P 4 fragment. 5 In the present paper, we report another radical process involving the phosphaalkene group and show that, under radiolysis, the -P=C< bond can give rise to a phosphoniumyl radical cation (R3P+').…”