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Nitrogen NMR study of some mesoionic oxadiazoles and thiadiazoles
Author(s) -
Jaźwiński Jarosław,
Staszewska Olga,
Wiench Jerzy W,
Stefaniak Lech,
Araki Shuki,
Webb Graham A.
Publication year - 2000
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 - 10.1002/1097-458x(200008)38:8<617::aid-mrc667>3.0.co;2-4
Subject(s) - mesoionic , chemistry , carbon 13 nmr , ab initio , chemical shift , computational chemistry , molecular orbital , thiadiazoles , crystallography , natural bond orbital , nuclear magnetic resonance spectroscopy , molecule , stereochemistry , density functional theory , organic chemistry
15 N chemical shifts are reported for 10 mesoionic oxadiazoles and thiadiazoles. Some supporting 14 N and 13 C NMR data are also reported, together with some ab initio molecular orbital calculations and x‐ray diffraction data. The relation between compound structure and 15 N chemical shifts is discussed. 14 N NMR measurements and ab initio molecular orbital calculations are employed to identify the charge distributions within the molecules studied. Some 1 J (C4,C5), 2 J ( 15 N, 13 C) and 1 J ( 15 N, 13 C) spin coupling data for mesoionic oxadiazoles, thiadiazoles and acetylosydnonimines are given. X‐ray diffraction data for the picrate of acetylsydnonimine and a 3,1,2,‐thiadiazole are reported. The bond lengths within the mesoionic backbone are intermediate between the values for single and double bonds, suggesting a conjugated bond system. The arrangement of the exocyclic group observed in the solid state for acetylosydnonimine corresponds to the arrangement predicted by solution NMR studies. Copyright © 2000 John Wiley & Sons, Ltd.