Question

In the reaction $2X+B_2{H}_6\to \left[B{H}_2{X}_2{]}^{+}\right[B{H}_4{]}^{-}$ the amine(s) X is (are) :

• A. $N{H}_3$
• B. $C{H}_{2}N{H}_2$
• C. $(C{H}_3{)}_{2}NH$
• D. $(C{H}_3{)}_{3}N$

Answer 1

Answer: (A), (B)

The correct options are
A $N{H}_3$
B $C{H}_{2}N{H}_2$

Diborane forms addition compounds with lewis bases as it is electron deficient compound act as lewis acid. If the lewis base is small without steric strain unsymmetric cleavage takes place. If the base is large with steric strain symmetric cleavage takes place.

$B_2{H}_6+N{H}_3\to \left[B{H}_2\right(N{H}_3{)}_2{]}^{+}[B{H}_4{]}^{-}\to B_3{N}_3{H}_6(Borazol)$

$B_2{H}_6+C{H}_{3}N{H}_2\to \left[B{H}_2\right(C{H}_{3}N{H}_2{)}_2{]}^{+}[B{H}_4{]}^{-}$

$B_2{H}_6+(C{H}_3{)}_{2}NH\to [B^{-}{H}_3-N^{+}H\left(C{H}_3{)}_2\right]\to \left[B{H}_{2}N\right(C{H}_3{)}_2]$

$B_2{H}_6+(C{H}_3{)}_{3}N\to [(C{H}_3{)}_3{N}^{+}-B^{-}{H}_3]$