MICROWAVE SPECTRA AND NUCLEAR QUADRUPOLE COUPLING IN $F_{3}B-N(CH_{3})_{3}$ AND $(CH_{3})_{3}B-N(CH_{3})_{3}$
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Date
1999
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Ohio State University
Abstract
The donor-acceptor complexes $F_{3}B-N(CH_{3})_{3}$ and $(CH_{3})_{3}B-N(CH_{3})_{3}$ have been studied by Fourier transform microwave spectroscopy. The rotational constants for both species are consistent with the literature values. For $F_{3}B-N(CH_{3})_{3}$, the $J=0-1$ and 1-2 transitions have been fully analyzed for the $^{10}B, ^{11}B, ^{14}N$ and $^{15}N$ species. A single state is observed, with no evidence of internal rotation. For $(CH_{3})_{3}B-N(CH_{3})_{3}$, the 0-1 and 1-2 transitions have been recorded and analyzed. In this case, two states are observed, with an intensity ratio of about 10:1. For both systems, a Townes and Dailey analysis of the $^{14}N$ nuclear quadrupole coupling constants has been used to provide information about the electronic structure of the complexes. In the case of $F_{3}B-N(CH_{3})_{3}$, about 0.6 electrons are transferred from the trimethylamine to the $BF_{3}$ upon formation of the donor-acceptor bond, while for $(CH_{3})_{3}B-N(CH_{3})_{3}$ a value of 0.42 electrons is obtained. These results will be compared with similar measurements for related adducts of ammonia and trimethylamine.
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Author Institution: Department of Chemistry, University of Minnesota