For higher boranes 3c-2e 'BBB' bond may be a part of their structures. In $\mathrm{B}_{5} \mathrm{H}_{9}$, the number of such electron deficient bond(s) present is/are
(a)four
(b)two
(c)zero
(d)one
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
B₅H₉ (styx 4120): four B–H–B bridges, one closed 3c-2e BBB bond, two B–B bonds — one BBB bond.