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Calculation of some boron nuclear screening constants
Author(s) -
Ebraheem K. A. K.,
Webb G. A.
Publication year - 1977
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.1270100160
Subject(s) - cndo/2 , boron , atomic orbital , chemical shift , chemistry , molecular orbital , atomic physics , charge density , anisotropy , effective nuclear charge , excitation , molecular physics , physics , molecule , nuclear physics , electron , quantum mechanics , organic chemistry , ion
Boron screening constants and their anisotropies have been calculated for 23 trivalent boron compounds. The calculations have been performed within a framework in which gauge‐dependent atomic orbitals are used in the molecular orbital description. Reasonable agreement with experimental chemical shifts is found when CNDO/S parameters are used; INDO calculations are less satisfactory. No correlation is found between the observed chemical shifts and those estimated from the Average Excitation Energy approach. Similarly, no correlation is found with total boron charge densities although agreement is reported with π charge density. In trimethylboron the lowest energy σ→π* transition dominates the in‐plane contributions to the local paramagnetic term while various σ→π* transitions dominate the out‐of‐plane contributions.