Isomérie Polyédrique dans des Spirophosphoranes Possédant le Groupement P?H

We have studied the temperature dependence of NMR spectra of six spirophosphoranes of the general formula: Experimental data show intramolecular isomerism which was explained by pseudo-rotation mechanism (Berry, Lit. 1). In all cases except one we also observed tautomerism between spirophosphorane and phosphite forms.