13C and 29Si NMR spectra and intramolecular interactions in derivatives of phosphaalkenes R-P=C[Si(CH3)3]2

Analysis of the ¹³C, ²⁹Si, and ³¹P NMR spectra in the series of C-bis(trimethylsilyl)phosphaalkenes made it possible to differentiate between the mechanisms of the electronic effects of the substituents R at the P atom on the -system of the -P=C(SiMe₃)₂ group. It was established that substituents R capable of n (or ) conjugation (NMe₂, OR, Hlg) substantially perturb the -system, destabilizing the levels of the occupied MO of the P=C bond; substituents with poorly defined -donating (accepting) characteristics (tert-Bu, iso-Pr, CN, Ph) only influence the investigated system through its polarization. Criteria which agree with the reactivity characteristics of the phosphaalkenes were obtained.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 6, pp. 729–733, November–December, 1988.