Boron, nitrogen, and fluorine nuclear quadrupole coupling and the electronic structure of the boron-nitrogen single bond

Abstract

The 11B and 19F nuclear quadrupole couplings in F3BNH x (CH 3) 3− x compounds were measured in the solid state by quadrupole perturbed nuclear magnetic resonance of boron and time-differential, perturbed angular distribution of the γ radiation of excited fluorine nuclei. The coupling constants are independent of the number of methyl substituents within experimental error both in the case of boron ( e 2qQ h = 80 ± 8 kHz ) and in the case of fluorine ( e 2gQ h = 30.0 ± 0.5 MHz ). Similarly, there is no change of the asymmetry F 3BNH(CH 3) 2, a boron asymmetry parameter of 0.30 ± 0.05 was found. Earlier results on the nitrogen quadrupole couplings in F 3BNH x R 3− x , and the nitrogen and boron couplings in H 3BNH x R 3− x compounds, extended by the present findings, provide a clear picture of the chemical bonding in these compounds, especially the donor-acceptor character and the ionicity of the boron-nitrogen bond.