A MULTINUCLEAR NMR-STUDY OF TAUTOMERIC EQUILIBRIA IN SOME IMINOPHOSPHINES

P-31 NMR data are reported for three iminophosphines in CDCl3 and (CD3)2CO solutions at a variety of temperatures. Due to the thermal instability of the compounds studied, it was not possible to heat the samples sufficiently to obtain the coalescence point in the P-31 spectrum taken at 202.4 MHz. The A half-arrow-right-over-half-arrow-left B tautomeric equilibrium is found to be strongly dependent upon solvent, temperature and substituent. The thermodynamic parameter DELTA-H favours form B and DELTA-S favours form A. C-13 NMR data support the conclusions drawn from the P-31 measurements.