• 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 )