15N, 31P, and 13C NMR Spectroscopy of N-Arylsulfonyl-and N-Arylcarbonyl-P,P,P-triphenylphospha-λ-Azenes. Substituent Effects and Electronic Structure

Abstract

Abstract The 15N, 31P and 31C NMR spectra of several series of phospha-λ5-azenes are reported. For the N-arylsulfonyl-P,P,P-triphenylphospha-δ5-azene series (R-C6H4N-SO2-PPh3), the 31P chemical shifts, various 13C chemical shifts and 1JPN were observed to correlate linearly with the Hammett σ constants. Interestingly, the 15N chemical shifts did not correlate acceptably with any σ or with the Taft dual substituent parameter equation, and 1JPC was invariant with substituent. For the N-arylcarbonyl-P,P,P-triphenylphospha-λ5-azene series (R-C6H4-CO-N=PPh3), δ31P and various δ13C's were observed to linearly correlate with the δ constants, while δ15N, 1JPN and 1JPC correlated with both the σ and σ constants. For the N-phenyl-P,P,P-triarylphospha-λ5-azene series [Ph-N=P(C6H4-R)3] the best correlations were observed between 31P, 15N and several 13C chemical shifts and the σ constants.