Knowledge Bank

The unstable molecule difluoroborane, $HBF2$, has been prepared in good yield by the reaction of $BF3$ with hot solid $NaBH4$ in a flow system attached directly to a 20 m multipass cell. Measurements of the $401$ c-type vibrational band have been made using a high resolution Bomem DA3.002 FTIR spectrometer with an apodized resolution of $0.004cm-1$. It has been found that the original assignment of the K $structure1$ is in error by one unit so that the value for $\nu 0$ has been increased by $\sim 3cm-1$. Detailed assignments of the fine structure have been made using rotational and centrifugal distortion constants for the ground state derived from the microwave spectrum, which has been remeasured to high values of J and K.