One- and two-dimensional multinuclear magnetic resonance study of azaphospholes; sign determination of J(15N, 1H), J(31P, 1H), J(31P, 13C), J(31P, 15N); Application of hahn-echo extended pulse sequences

✍ Scribed by Bernd Wrackmeyer; ĒRiks Kupče; Alfred Schmidpeter

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 555 KB
• Volume: 29
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260291013

✦ Synopsis

Abstract

Various 1,2,3‐ and 1,3,4‐diazaphospholes (1 to 4), a 1,2,3,4‐triazaphosphole (5) and two 1,2,3‐diazaphospholium chlorides (6, 7) have been studied by ^13^C, ^15^N and ^31^P NMR spectroscopy. The absolute signs [based on ^1^J(^13^C, ^1^H) > 0] of numerous coupling constants [e.g., ^1^J(^31^P, ^13^C) < 0, ^1^J(^31^P, ^15^N) > 0] have been determined by combining information from one‐dimensional selective ^1^H{^31^P}, ^13^C{^31^P} and two‐dimensional (2D) ^13^C/^1^H, ^15^N/^1^H and ^31^P/^1^H heteronuclear shift correlations. __H__ahn‐__e__cho e__xtende__d (HEED) pulse sequences have been applied to one‐ and two‐dimensional ^31^P NMR measurements. In 1D ^31^P NMR spectra, ^1^J(^31^P, ^15^N) coupling constants can be conveniently determined. The corresponding HEED 2D ^31^P/^1^H experiments yield, in addition, the long range ^n^J(^15^N^1^H) (n = 2,3) coupling constants (and their relative signs). Furthermore, isotope shifts, ^1^Δ^15/14^N, on ^31^P resonances were measured. The low frequency shifts (−0.072 to −0.114 ppm) observed here for two‐coordinate phosphorus compounds 1 to 7 are much larger than those previously reported for P(V)‐ and three‐coordinate P(III) compounds.