CHTP 42
Boranes
Hydrides of boron are generally known as Boranes
Their general formula is BxHy
The parental member of this family is BH3 (Which is stable only in
gaseous state)
All the boranes are gaseous substance at ordinary temperature
01
They are not stable and readily oxidized in air (When comes in
4
94
contact with air)
70
The higher boranes consist of the boron cluster
56
Classification of boranes :
19
Boranes can be classified into five structural categories:
-9
1. Closo-boranes (from Greek: cage like):
Y
They have complete closed polyhedral structure with trigonal faces
H
AT
(football like structure).
General formula of closo borane is BnH n+2 or BnH n+1 -1 or BnHn2-
EV
eg: B6H62-
R
2. Nido-boranes (from Latin: nest like):
They have non-closed structures in which the boron cluster
occupies n corners on an (n + 1) cornered polyhedron.
General formula of nido borane is BnH n+4 or BnH n+3 -1 or
BnHn+22-
eg: B5H9, B6H10
3. Arachno-boranes (from Greek: spider’s web like):
They have even more open cluster in which the B atoms
occupy n contiguous corners of an (n + 2)-cornered
polyhedron.
1
, General formula of arachno borane is BnH n+6 or BnH n+5-1 or
BnHn+42-
eg: B5H11
4. Hypho-boranes (from Greek: net like):
They have the most open clusters in which the B atoms occupy n
corners on an (n + 3)-cornered polyhedron.
General formula of hypo borane is BnH n+8
5. Klado boranes :
In which the B atoms occupy n corners on an (n + 4)-cornered
polyhedron
01
General formula BnH n+10
4
94
70
56
19
-9
Y
H
AT
Diborane (B2H6)
EV
• It is the simplest and most studied among the hydrides
R
• It is used to prepare the higher boranes and is an important reagent
in synthetic organic chemistry
• It is a versatile reagent for production of organoboranes which are
useful intermediates in organic synthesis
Preparation
Stock’s method
Mg and B heated to give Mg3B2 (Magnesium boride) and then
heated with phosphoric acid.
2
Boranes
Hydrides of boron are generally known as Boranes
Their general formula is BxHy
The parental member of this family is BH3 (Which is stable only in
gaseous state)
All the boranes are gaseous substance at ordinary temperature
01
They are not stable and readily oxidized in air (When comes in
4
94
contact with air)
70
The higher boranes consist of the boron cluster
56
Classification of boranes :
19
Boranes can be classified into five structural categories:
-9
1. Closo-boranes (from Greek: cage like):
Y
They have complete closed polyhedral structure with trigonal faces
H
AT
(football like structure).
General formula of closo borane is BnH n+2 or BnH n+1 -1 or BnHn2-
EV
eg: B6H62-
R
2. Nido-boranes (from Latin: nest like):
They have non-closed structures in which the boron cluster
occupies n corners on an (n + 1) cornered polyhedron.
General formula of nido borane is BnH n+4 or BnH n+3 -1 or
BnHn+22-
eg: B5H9, B6H10
3. Arachno-boranes (from Greek: spider’s web like):
They have even more open cluster in which the B atoms
occupy n contiguous corners of an (n + 2)-cornered
polyhedron.
1
, General formula of arachno borane is BnH n+6 or BnH n+5-1 or
BnHn+42-
eg: B5H11
4. Hypho-boranes (from Greek: net like):
They have the most open clusters in which the B atoms occupy n
corners on an (n + 3)-cornered polyhedron.
General formula of hypo borane is BnH n+8
5. Klado boranes :
In which the B atoms occupy n corners on an (n + 4)-cornered
polyhedron
01
General formula BnH n+10
4
94
70
56
19
-9
Y
H
AT
Diborane (B2H6)
EV
• It is the simplest and most studied among the hydrides
R
• It is used to prepare the higher boranes and is an important reagent
in synthetic organic chemistry
• It is a versatile reagent for production of organoboranes which are
useful intermediates in organic synthesis
Preparation
Stock’s method
Mg and B heated to give Mg3B2 (Magnesium boride) and then
heated with phosphoric acid.
2
