Abstract
A series of phosphoranyl radicals, produced by addition of photochemically generated alkoxyl or benzoyloxyl radicals to substituted 1,3,2-dioxaphospholans, have been studied by e.s.r. spectroscopy. The spectra of certain of these radicals exhibit line-shape effects which are interpreted in terms of intramolecular ligand exchange at phosphorus. On the basis of deuterium labelling studies, two types of apical–equatorial ligand exchange have been identified, involving interchange of exocyclic or of endocyclic substituents, respectively. The spectra derived from 4,4-dimethyl-1,3,2-dioxaphospholans show the presence of an approximately equimolar mixture of two isomeric phosphoranyl radicals, in, which the endocyclic CH2O group is sited either apically or equatorially. The e.s.r. spectra of some cyclic and acyclic phosphoranyl radicals show that, in general, ligand apicophilicity decreases in the order F–, Cl–, RC(O)O–>[graphic omitted]–, OCN–> RO–, R2N>H–>H3C–, closely paralleling group electronegativity. Rate constants for exchange of apical with equatorial H and Me2N ligands, repectively, in the acyclic radicals H2(Me)ṖOBut and (Me2N)2ClṖOBut have been estimated.
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Schedule a callMore From: Journal of the Chemical Society, Perkin Transactions 2
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