• INUDUSTRIAL PREPERATION:-2BF3( g) + 6LiH( s) → B2H6( g) + 6LiF( s)
• Laboratory method:
( i) By the reaction of iodine with sodium borohydride in a high boiling solvent.
2NaBH4 + I2 → B2H6 + 2NaI + H2( ii) By reduction of BCl3 with LiAlH4
4BCl3 + 3LiAlH4 → 2 B2H6 + 3AlCl3 + 3 LiCl
Structure of Diborane, B 2 H 6
Some important characteristics of boranes:
i) Lower boranes are colourless gases while higher boranes are volatile liquids or solids.
ii) They undergo spontaneous combustion in air due to strong affinity of boron for oxygen.
B2H6 + 3O2 → B2O3 + 3H2O + Heat
iii) Boranes react with alkali metal hydrides in diethyl ether to form borohydride complexes.
B2H6 + 2MH →2M + [ BH4 ]-( M = Li or Na)