2. Methods Of Preparetion
 It is the simplest boron hydride. It is prepared by treating
boron Trifluoride with LiAlH4 in diethyl ether
4BF3 + 3LiAlH4 2B2H6 +3LiF + 3ALF3
 In a laboratory the diborane is prepared by the oxidation of
sodium borobhydride with iodine
2NaBH4 + I2 B2H6 +2NaI +H2
 In industry it is prepared by the reaction of BF3 with
sodium hydride
2 BF3 + 6 NaH 450 K B2H6 + 6 NaF

3. PRORPERTIES
1) Diborane is a colorless, highly toxic gas. It has boiling
point ok 180 K
1) Diborane catches fire spontaneously when it is exposed
to atmospheric air
it burns with oxygen. The reaction is exothermic
releasing a lager amount of energy
B2H6 + 3O2 B2O3 + 3H2O
ΔH= - 1976 K J mol-1
3) it is readily hydrolyzed by water to form boric acid
B2H6 + 6H2O 2B(OH)3 + 6H2

4. 4) With Lewis bases, diborane first undergoes cleavage
(breaking) to form borane (BH3) which then reacts to
form adducts
B2H6 + 2NMe 2BH3 . NMe
B2H6 + 2CO 2BH3 . CO
5) with ammonia an addition product B2H6.NH3formulated
as [ BH2(NH3)2]+ [BH4]- is formed which then
decomposes on heating at 473K to give a volatile
compound called borazole (Borazine)
3 B2H6 + 6NH3 [ BH2(NH3)2]+ [BH4]- 473K
2B3N3H6 + 12H2
( borazole)

5. BORAZOLE (BORAZINE)
 This compound is called inorganic benzene in view of
its ring structure with alternate NH and BH groups.
Borazole contains 3 double bonds and has 6 electron
system which is similar to benzene

6. 6)Many metal hydrides react with diborane to form
tetrahydridoborate which contain [BH4]- tetrahedral
ion.
 2MH + B2H6 2M+ [BH4]-
 Where (M=Li or Na), for ex:
 2LiH + B2H6 2Li+ [BH4]-

7. STRUCTURE OF DIBORANE
 X-ray diffraction has shown the following structure of
diborane
 Here B atoms undergo sp3 hybridization. There are
four terminals B-Ht normal covalent bonds which are
quite strong and two bridge B……Hb…..B which are
different from normal covalent bonds and are quite
weak
 The four Ht molecules and b atoms lie in the same
plane while one Hb lies above and one below the plane

8.  As there are 12 electrons and 8 bonds in B2H6 molecule
it is an electron deficient molecule
 Because of their resemblance to a banana these are
also called banana bonds shown in the structure.
 Hence diborane molecule has two electrons less than
the maximum required number thus it is an electron
deficient molecule

9. USES OF DIBORANE
 Diborane has been suggested as a rocket
propellant and experimentally fired but not used in
any in service rocket as a rubbervulcaniser as
a catalyst for hydrocarbon polymerization as a
flame-speed accelerator, and as a doping agent for the
production of semiconductors. It is also an
intermediate in the production of highly
pure boron for semiconductor production. It is also
used to coat the walls of tokomaks to reduce the
amount of heavy metal impurities in the plasma.

10. The End