Knowledge Bank

The donor-acceptor complexes $F3B-N(CH3)3$ and $(CH3)3B-N(CH3)3$ have been studied by Fourier transform microwave spectroscopy. The rotational constants for both species are consistent with the literature values. For $F3B-N(CH3)3$, the $J=0-1$ and 1-2 transitions have been fully analyzed for the $\mathrm{<mrow\; data-mjx-texclass="ORD">10</mrow>}B,11B,14N$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N$ species. A single state is observed, with no evidence of internal rotation. For $(CH3)3B-N(CH3)3$, 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 $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N$ nuclear quadrupole coupling constants has been used to provide information about the electronic structure of the complexes. In the case of $F3B-N(CH3)3$, about 0.6 electrons are transferred from the trimethylamine to the $BF3$ upon formation of the donor-acceptor bond, while for $(CH3)3B-N(CH3)3$ a value of 0.42 electrons is obtained. These results will be compared with similar measurements for related adducts of ammonia and trimethylamine.