Structural and electronic studies of substituted m-terphenyl lithium complexes.
Dalton Trans
; 50(2): 722-728, 2021 Jan 14.
Article
em En
| MEDLINE
| ID: mdl-33346293
ABSTRACT
The effect of para-substitution upon the structural and electronic properties of a series of m-terphenyl lithium complexes [R-Ar#-Li]2 (R = t-Bu 1, SiMe32, H 3, Cl 4, CF35; where R-Ar# = 2,6-{2,6-Xyl}2-4-R-C6H2 and 2,6-Xyl = 2,6-Me2C6H3) has been investigated. X-ray crystallography reveals the complexes to be structurally similar, with little variation in C-M-C bond lengths and angles across the series. However, in-depth NMR spectroscopic studies reveal notable electronic differences, showing a linear correlation between the 7Li{1H} NMR chemical shifts of the para-substituted complexes and their Hammett constants. The flanking methyl protons exhibit a similar electronic shift in the 1H NMR spectra, which has been rationalised by the presence of through-space LiH interactions, as evidenced by two-dimensional 7Li-1H heteronuclear Overhauser spectroscopy (HOESY). In both cases, electron-withdrawing substituents are found to cause an upfield peak shift. A computational analysis is employed to account for these trends.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Ano de publicação:
2021
Tipo de documento:
Article