13C and31P NMR study of phosphoranes containing 1,3,2-dioxa- and 1,3,2-oxazaphospholene rings and bipolar ions related to them

1. Direct proof for the phosphorotropic tautomerism, where compounds with a pentacoordinated phosphorus atom are in equilibrium, was obtained from the comparative analysis of temperature dependences of13C and31P NMR spectra of phosphoranes containing 1,3,2-dioxa- and 1,3,2-oxazaphospholene rings, and related bipolar ions. 2. Free energies of activation of the phosphorotropic rearrangement were determined. © 1985 Plenum Publishing Corporation.