Multinuclear NMR Studies of the Substitlent Effects in N-Phenyl-P,P,P-Triarylphospha-λ5-Azenes, Triaryl-Phosphines and Triarylphosphine Oxides

Abstract

Abstract A series of N-phenyl-P,P,P-triarylphospha-λ5-azenes (1) as well as their l5N labeled analogs was synthesized. The 13C, 31P, and 15N NMR spectra of this series and those of two other series of related compounds, namely triarylphosphines (2) and triarylphosphine oxides (3), were measured and are reported. Many satisfactory correlations using the mono-substituent parameter (MSP) and the Taft dual-substituent parameter (DSP) treatments with the 13C substituent chemical shifts (SCS), 31P SCS, 15N SCS and the one bond P-N, P-C and C-N coupling constants were observed and will be discussed. Thus, for example, the 31P and 15N chemical shifts in 1 correlated with [sgrave]−with negative slopes while the 31P chemical shifts in 3 correlated with those in 1 with a slope of 2.0. The 13C chemical shifts in 1 correlated excellently with the corresponding ones in 3 with slopes very close to unity. The substituent effects on the chemical shifts of the various nuclei were shown to be mainly due to changes in the ch...