The consequences of R3B coordination (R = Me, Et, cyclohexyl) to nitrogen-contg. anion radicals and of Mes2B substitution (Mes = mesityl) at C or N p centers of radical ions were studied for a series of closely related carbo- and heterocyclic p systems by ESR/ENDOR spectroscopy. Examples include the anion radicals of dinuclear R3B coordination compds. with pyrazine and 4,4'-bipyridine, para-diboryl-substituted benzene, and biphenyl radical anions and the correspondingly substituted 1,4-dihydropyrazine and 1,1'-dihydro-4,4'-bipyridine radical cations. Whereas the perturbation of spin distribution is most pronounced for the dimesitylboryl-substituted homoarom. anions, the isoelectronic cations of the non-arom. Mes2B-substituted dihydroheterocyles exhibit a substantial decrease of the heteronuclear (11B, 14N) ESR/ENDOR coupling consts. owing to a considerable degree of B/N p bonding. MO/McLachlan perturbation calcns. suggest that both the orbital overlap and the electronegativity differences contribute to the obsd. effects. on SciFinder(R)
%0 Journal Article
%1 Lichtblau.1992
%A Lichtblau, Alexander
%A Kaim, Wolfgang
%A Schulz, Andreas
%A Stahl, Thomas.
%D 1992
%J Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry
%K ENDOR ENDOR;carbon ESR bond boron effect ion ion;ESR organo organoboron organoboron;nitrogen radical substituent
%N 9
%P 1497--1501
%T Organoboron substituent effects in EPR/ENDOR spectroscopy. Radical ions with boron-carbon and boron-nitrogen bonds
%X The consequences of R3B coordination (R = Me, Et, cyclohexyl) to nitrogen-contg. anion radicals and of Mes2B substitution (Mes = mesityl) at C or N p centers of radical ions were studied for a series of closely related carbo- and heterocyclic p systems by ESR/ENDOR spectroscopy. Examples include the anion radicals of dinuclear R3B coordination compds. with pyrazine and 4,4'-bipyridine, para-diboryl-substituted benzene, and biphenyl radical anions and the correspondingly substituted 1,4-dihydropyrazine and 1,1'-dihydro-4,4'-bipyridine radical cations. Whereas the perturbation of spin distribution is most pronounced for the dimesitylboryl-substituted homoarom. anions, the isoelectronic cations of the non-arom. Mes2B-substituted dihydroheterocyles exhibit a substantial decrease of the heteronuclear (11B, 14N) ESR/ENDOR coupling consts. owing to a considerable degree of B/N p bonding. MO/McLachlan perturbation calcns. suggest that both the orbital overlap and the electronegativity differences contribute to the obsd. effects. on SciFinder(R)
@article{Lichtblau.1992,
abstract = {The consequences of R3B coordination (R = Me, Et, cyclohexyl) to nitrogen-contg. anion radicals and of Mes2B substitution (Mes = mesityl) at C or N \textgreek{p} centers of radical ions were studied for a series of closely related carbo- and heterocyclic \textgreek{p} systems by ESR/ENDOR spectroscopy. Examples include the anion radicals of dinuclear R3B coordination compds. with pyrazine and 4,4'-bipyridine, para-diboryl-substituted benzene, and biphenyl radical anions and the correspondingly substituted 1,4-dihydropyrazine and 1,1'-dihydro-4,4'-bipyridine radical cations. Whereas the perturbation of spin distribution is most pronounced for the dimesitylboryl-substituted homoarom. anions, the isoelectronic cations of the non-arom. Mes2B-substituted dihydroheterocyles exhibit a substantial decrease of the heteronuclear (11B, 14N) ESR/ENDOR coupling consts. owing to a considerable degree of B/N \textgreek{p} bonding. MO/McLachlan perturbation calcns. suggest that both the orbital overlap and the electronegativity differences contribute to the obsd. effects. [on SciFinder(R)]},
added-at = {2019-07-15T13:41:23.000+0200},
author = {Lichtblau, Alexander and Kaim, Wolfgang and Schulz, Andreas and Stahl, Thomas.},
biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2e52d96d8808cb12ec083a2a38ed13f55/b_schwederski},
interhash = {ef95918293466c1d3ed653afae77fe36},
intrahash = {e52d96d8808cb12ec083a2a38ed13f55},
issn = {0300-9580},
journal = {Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry},
keywords = {ENDOR ENDOR;carbon ESR bond boron effect ion ion;ESR organo organoboron organoboron;nitrogen radical substituent},
number = 9,
pages = {1497--1501},
timestamp = {2019-07-15T11:42:10.000+0200},
title = {Organoboron substituent effects in EPR/ENDOR spectroscopy. Radical ions with boron-carbon and boron-nitrogen bonds},
year = 1992
}
