The 1H, 13C and 31P NMR spectra of EZ pairs of some phosphorus substituted alkenes

The olefins Ph2P(X)CHCHR [X=lone pair, O, S, Ch3I; RCh3, ph, P(X)ph2] have been prepared and their 1H, 13C and 31P NMR spectra measured. trans 3J[P(IV)C] (range 18.3–25.7 Hz) is greater than cis 3J[P(IV)C] (range 6.9–11 Hz) but this relationship does not hold for P(III) compounds. In the 31P spectra the E isomer absorbs to higher field than the Z isomer for P(III) and P(IV) compounds. The 1H data are in accord with previous results; average substituent shielding coefficients for ph2P(X) substituted alkenes are reported.