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13 C NMR spectra of phosphole–P(IV) dimers; ABX and AA′X 13 C 31 P coupling in some derived structures
Author(s) -
Quin Louis D.,
Mesch Keith A.,
Bodalski Ryszard,
Pietrusiewicz K. Michal
Publication year - 1982
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270200205
Subject(s) - chemistry , nmr spectra database , spectral line , dimer , chemical shift , crystallography , intramolecular force , nuclear magnetic resonance spectroscopy , multiplet , coupling constant , nuclear magnetic resonance , stereochemistry , physics , organic chemistry , particle physics , astronomy
The easily obtained dimers of phosphole oxides, sulfides and methiodides give 13 C NMR spectra where carbons within three (sometimes four) bonds of each 31 P nucleus are doublets of doublets and thus constitute X in an AMX spectrum. Most of the spectra have been completely interpreted with the aid of spectral measurements at two magnetic fields. Saturation of the double bonds in dimers of methylphosphole–P(IV) derivatives causes the 31 P nuclei to have very similar chemical shifts, with Δν not adequately different from 3 J (PP) to give first‐order coupling. When both 31 P nuclei couple with a given 13 C, a second‐order (ABX) 31 C NMR spectrum is obtained. The presence of the effect is revealed by running the 13 C NMR spectra at high magnetic field; J (AX)+ J (BX) is constant at all fields, but spacing between the lines of the multiplet varies. The spectrum of the oxide, with Δν/ J =1.44 for the 31 P spectrum at 36.43 MHz, approaches first order character at 75 MHz; the methiodide spectrum (Δν/ J =4.55) is second order at 15 MHz but clearly first order at 50 MHz, and the sulfide (Δν/ J =5.6) is nearly first order at 15 MHz. [2 + 2]‐Photochemical intramolecular cyclization of the dimer oxides provides cage‐like structures where the 31 P nuclei are chemically equivalent, but magnetically non‐equivalent, making the 13 C signals have the characteristics of X in an AA′X coupling pattern.