The observed bond length in () is significantly shorter than the theoretical value calculated for a — Chemical Bonding Chemistry Question

💡 Solution & Explanation

Both Boron and Fluorine have $2p$ orbitals. Boron has a vacant $2p$ orbital, and Fluorine has full $2p$ lone pairs. Effective sideways overlapping occurs, creating a $p\pi-p\pi$ back bond (dative $\pi$ -bond) that gives the $B-F$ connections partial double-bond character, substantially shortening them.