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Measurement of indirect spin—spin coupling constants between crystallographically equivalent nuclei. Determination of 2 J ( 31 P, 31 P) in solid Ag[P( m ‐tolyl) 3 ] 2 NO 3
Author(s) -
Wu Gang,
Wasylishen Roderick E.,
Pan Hongjun,
Liu C. W.,
Fackler John P.,
Shang Maoyu
Publication year - 1995
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260330908
Subject(s) - chemistry , magic angle spinning , nmr spectra database , coupling constant , chemical shift , phosphorus 31 nmr spectroscopy , nuclear magnetic resonance spectroscopy , spin (aerodynamics) , crystallography , spectral line , analytical chemistry (journal) , solid state nuclear magnetic resonance , magic angle , nuclear magnetic resonance , stereochemistry , physics , particle physics , astronomy , thermodynamics , chromatography
Solid‐state 31 P magic angle spinning (MAS) NMR spectra of Ag[P( m ‐tolyl) 3 ] 2 NO 3 were investigated as a function of the magic angle spinning frequency. Examination of the 31 P MAS NMR spectra obtained at 4.70 and 9.40 T indicates that the two phosphorus nuclei have identical isotropic chemical shifts, that is, they are crystallo‐graphically equivalent, δ = 11.2 ppm. However, since the orientation of their respective chemical shift tensors is not coincident, the two phosphorus nuclei are magnetically non‐equivalent and exhibit spinning‐frequency dependent 31 P NMR lineshapes. Analysis of the spinning‐frequency dependent 31 P MAS NMR spectra at 4.70 and 9.40 T indicates that 2 J ( 31 P, 31 P) = 140 Hz. This value was confirmed by 2D J ‐resolved spectroscopy. The determination of an indirect spin‐spin coupling constant between two nuclei which constitute an ‘isolated’ spin pair with identical isotropic chemical shifts is not possible in conventional solution‐state NMR studies unless a third spin is introduced. The 31 P MAS NMR spectra of Ag[P( m ‐tolyl) 3 ] 2 NO 3 also exhibit resolvable splittings due to 109 Ag and 107 Ag; 1 J ( 109 Ag, 31 P) = 517±5 Hz and 1 J ( 107 Ag, 31 P) = 453 ± 5 Hz. In solution NMR studies these couplings are not always observed because of rapid metal‐ligand exchange.