Application of Hahn‐echo extended pulse sequences to phosphorus–nitrogen compounds. Determination of coupling signs and detection of 15N31P15N isotopomers in natural abundance

Abstract

AbstractHahn‐echo extended (HEED) pulse sequences in one‐ and two‐dimensional experiments were successfully applied to phosphorus–nitrogen compounds with two PN bonds {2‐chloro‐1,3‐dimethyl‐1,3,2‐diazaphospholidine (1), 2‐tert‐butyl‐1,3‐dimethyl‐1,3,2‐dizaphospholidine (2), bis(diethylamino)chlorophosphane (3) and bis(diethylamino)phosphenium cation (4; counterion [AlCl4]−)}. In the case of 2, the 31P resonance signal was detected as a sharp triplet for the 15N31P15N isotopomer in natural abundance: the secondary isotope effect on the coupling constant 1J(31P15N) in 14N31P15N and 15N31P15N isotopomers is < 0.05 Hz; the isotope‐induced shifts 1Δ 15/14N(31P) are additive. The value of 1Δ 15/14N(31P) in the phosphenium cation 4 is markedly more negative than that in its precursor 3 or other aminophosphanes. For 2, the absolute signs of the coupling constants 2J(15N 1H) ( < 0), all 3J(31P1H) ( > 0), 1J(31PC13C) ( < 0), 2J(31PC13C) ( > 0), 2J(31PN 13CCH3) ( > 0) and 2J(31PNCCH2) ( < 0) were determined using 1H detected 2D inverse pseudo triple resonance 1H{(13C)31P} experiments and 2D 13C1H, 15N1H and 31P1H heteronuclear shift correlations.