In the reaction

$2\mathrm{X}+{\mathrm{B}}_2{\mathrm{H}}_6⟶{\left[{\mathrm{BH}}_2{\mathrm{X}}_2\right]}^{\oplus }{\left[{\mathrm{BH}}_4\right]}^{⊝}$

the amine(s) X is (are)

$$\begin{gathered} \mathrm{when} \mathrm{X}\text{ is} \\ {\mathrm{NH}}_{{3 }_{ }}---{-}_{ } 2{\mathrm{NH}}_3+{\mathrm{B}}_2{\mathrm{H}}_6⟶{\left[{\mathrm{BH}}_2{\left({\mathrm{NH}}_3\right)}_2\right]}^{\oplus }{\left[{\mathrm{BH}}_4\right]}^{\ominus } \\ {\mathrm{CH}}_3{\mathrm{NH}}_2---- 2{\mathrm{CH}}_3{\mathrm{NH}}_2+{\mathrm{B}}_2{\mathrm{H}}_6⟶{\left[{\mathrm{BH}}_2{\left({\mathrm{CH}}_3{\mathrm{NH}}_2\right)}_2\right]}^{\oplus }{\left[{\mathrm{BH}}_4\right]}^{\ominus } \\ {\left({\mathrm{CH}}_3\right)}_2\mathrm{NH}--- 2{\{ {\left({\mathrm{CH}}_3\right)}_2\mathrm{NH} \}}_{ }+{\mathrm{B}}_2{\mathrm{H}}_6⟶{\left[{\mathrm{BH}}_2{\{ {\left({\mathrm{CH}}_3\right)}_2\mathrm{NH} \}}_2\right]}^{\oplus }{\left[{\mathrm{BH}}_4\right]}^{\ominus } \\ where as with teritiary amine {\left({\mathrm{CH}}_3\right)}_3\mathrm{N} \mathrm{with} {\mathrm{B}}_2{\mathrm{H}}_6\text{ forms an adduct: } \\ 2 {\left({\mathrm{CH}}_3\right)}_3\mathrm{N}+{\mathrm{B}}_2{\mathrm{H}}_6⟶2 \left[{\left({\mathrm{CH}}_3\right)}_3\mathrm{N}⟶{\mathrm{BH}}_3\right] \end{gathered}$$