Question

How is diborane prepared ? Explain its structure .

[ With Diagram ] ​

Answer 1

$\huge\bf{Answer:-}$

Refer the attachment.

Answer 2

Answer:

Preparation of diborane :-

a) Industrial Method :-

1) In industries diborane is prepared by the reaction between Boran trifluoride ( BF3 ) and sodium hydride ( NaH )

2BF3 + 6NaH ==> B2H6 + 6NaF [ 450 k ]

b) Laboratory Method :-

2) It is prepared by treating Boran trifluoride with LiAlH4 in dry ether .

4BF3 + 3LiAlH4 ==> B2H6 + 3LiF + 3AlF3

Structure of diborane :-

Diborane ( B2H6 ) is an electron deficient compound .

In B2H6 the four hydrogens present in two BH2 groups are known as terminal hydrogen atoms ( Ht ) . The remaining two H-atoms are called bridged hydrogen atoms ( Hb ) .

In diborane the central atom is Boran .

Ground state Electronic configuration of Boran atom is 1s² , 2s² , 2p¹x , 2p0y , 2p0z

Excited state Electronic configuration of Boran atom is 1s² , 2s¹ , 2p¹x , 2p¹y , 2p0z [ sp³ hybridisation ] .

In excited state Boran atom undergoes sp³ hybridisation , as a result 4-sp³ hybrid orbitals are formed . Out of these four hybrid orbitals one hybrid orbital is vacant , the remaining are half filled orbitals .

Each Boran atom makes two sigma bonds with 1s-orbital of hydrogen atom .

These bonds are called terminal bonds or 2-centered-2-electron bonds .

The two central Boran atoms makes two bridge bonds with the hydrogen atoms . In brigde bond formation the vacant sp³ hybrid orbital of one Boran atom and 1s orbital of hydrogen atom and half filled sp³ hybrid orbital of another Boran atom are participated. These bonds are known as B-H-B Bridge bonds or Banana bonds or 3-centered-2-electron bonds .

The B-H Terminal bonds lie in the same plane and the B-H-B Bridge bonds lie perpendicular to the plane of two BH3 groups .