question_answer

Why B-X bond distance in \[B{{X}_{3}}\] is shorter than theoretically expected value?

Answer:

                This is due to \[p\pi -p\pi \] back bonding of the fully filled p-orbital of halogen (X) into the empty p-orbital of boron (Fig. 11.5, page 11/13). As a result, B-X bond has some double bond character (Fig. 11.6, page 11/13)and hence B-X bond is shorter than expected.