CHEMICAL PROPERTIES OF DIBORANE:

The Boranes unddergo different type of chemical reactions like oxidation, pyrolysis, Nucleophilic and electrophic  and reactions with bases such as OH^- and NH₃.

(1) Reaction with Na: Diborane reacts with sodium amalgum to form an addition product B₂H₆Na₂.

(2) Reaction with air: the reaction of diborane with oxygen is highly exothermic and due to evolution of enormous amount of heat energy it can use as industrial fuel and propellants and not use as domestic due to its poisonous nature..

(3) Thermal Stability: B₂H₆ stable only at low temperature when heated 100 to 250 degree it changes into higher hydrides and On heating to 700ºC diborane dissociates.

Note: - Formation of B₂H₂Cl₄ shows that the 2H left in B₂H₂Cl₄ are responsible for dimmer formation (Bridge bond). Diborane has only four replaceable hydrogen and with their replacement, the dimeric structure continuous to be as such. Remaining  two hydrogen when they get displaced, the dimeric structure break indicating that these two hydrogen are act as bridging hydrogen.  

(9) Reaction with Ammonia (NH₃):

(1) Diborane react with excess NH₃ at temperature to form (inorganic graphite) Boron nitride (BN) _x.while when diborane and NH₃ react in 1:2 ratios at low temperature give   Inorganic Benzene (Borazole).

(2) Diborane is electron-deficient molecule and hence it reacts with several molecules having lone pair(s) of electron like CO, ether, amines, to form complex compounds.

(3) B₂H₆ give symmetrical cleavage with respect to only large size and weak amines CO, H¯, N(CH₃)₃ , THF, PH₃, PF₃ , OEt₃ OMe₂ ,Pyridine, Thiophene ,SMe₂, Set₃ etc.

(4) In the presence of small and strong base B₂H₆ undergo unsymmetrical cleavage like NH₃, H₂N (CH₃), HN (CH₃)₂ etc

ILLUSTRATIVE EXAMPLE:

(10) Methylation of Doborane:

(1) In diborane two boron atoms and four terminal hydrogen atoms lie in one plane. While two bridge hydogen atoms (encircled ) lie smmetrically above and below the plane.

(2) Total valence electrons in B₂H₆ is 12(6 from boron 3x2) and 6 from six hydrogen atoms) and there are two B-H-B (3C-2e) bridge bonds and four B-H (2C-2e) terminal bonds.

(3) Bond energy of B-H-B bond is 441 kjpermole which greater than bond energy B-H bond (341Kjpermole) hence methylation of diborane no more than four hydrogen.

(4) In above reaction it is clearly reveal that none of the bridge hydrogen in B₂H₆  has been replaced by –CH₃ .ie in this reaction both the bridge bond remaine undissociate.

Structure of "Inorganic Benzene" /Borazole/Borazine:

Structure of Boron Nitride:

Structure of Fulelrences:

Structure of Graphite: