Proton and Fluorine NMR Spectra of HBF2

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Abstract
Proton and fluorine NMR spectra of HBF2 were recorded in the temperature range 140°K to 230°K. The values for the spin‐coupling constants J HF, J 11 B—H and J 11 B—F are 108±1 Hz, 211±2 Hz, and 84±1 Hz, respectively. J HF is temperature independent. The apparent values of J 11 B—H and J 11 B—F decrease below 165°K due to the interaction of rapidly fluctuating electric field gradients with the electric quadrupole moment of boron. The center of the proton multiplet is about 0.12 ppm downfield from the center of the terminal proton multiplet in diborane. The fluorine multiplet is about 60 ppm downfield from the fluorine resonance in BF3, which in this case was a single structureless line. The dependence of 11B–H coupling constants on the orbital hybridization of boron is discussed.