A mixture of boron trichloride and hydrogen is subjected to silent electric discharge to form 'A' and HCI. 
'A' is mixed with NH₃; and heated to 200°C to form 'B'. The formula of 'B' is

When boron trifluoride undergoes in electric discharge in the presence of hydrogen gas, it forms B₂H₆ (A) and HCl.

$2{\mathrm{BCl}}_3+6{\mathrm{H}}_2\stackrel{\mathrm{Electric} \mathrm{discharge}}{\to }\underset{\left(\mathrm{A}\right)}{{\mathrm{B}}_2{\mathrm{H}}_6}+6\mathrm{HCl}$

When B₂H₆ (A) heated with ammonia at $200°\mathrm{C}$, it forms B₃N₃H₆ (B) and hydrogen gas. 

$3{\mathrm{B}}_2{\mathrm{H}}_6+6{\mathrm{NH}}_3\stackrel{200°\mathrm{C}}{\to }\underset{\left(\mathrm{B}\right)}{2{\mathrm{B}}_3{\mathrm{N}}_3{\mathrm{H}}_6}+12{\mathrm{H}}_2$