THE VIBRATIONAL SPECTRA, STRUCTURE, AND NATURE OF THE P:N BOND IN N,P,P,P-TETRAMETHYLPHOSPHINE IMIDE AND N-METHYL-$d_{3}$ -P,P,P-TRIMETHYLPHOSPHINE IMIDE

Abstract

The vibrational spectra of the compound N,P,P,P-tetramethylphosphine imide and its N-methyl-$d_{3}$ analogue have been found to be consistent only with a $C_{s}$ structure whose vibrational potential function exhibits large deviations from local $C_{3v}$ symmetry at both phosphorus and nitrogen. All 48 vibrational fundamentals expected under $C_{s}$ molecular point symmetry have been assigned based on group frequencies, isotopic frequency shifts, and Raman depolarization measurements. The P:N torsional modes have been assigned at 112 and $100 cm^{-1}$ in the light and heavy molecules, respectively, and threefold barriers of 2.06 and 2.42 kcals/mole, respectively, have been calculated from these assignments.