Applications Of Valence Bond Theory (VBT)
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| Applications Of Valence Bond Theory (VBT) |
VBT
has application for coordination compounds like octahedral and tetrahedral complexes.
Application of VBT for six-coordinated complexes or Octahedral complexes:
Those
complexes to which 6 ligands are attached to the central metal atom/ ion making
90⁰ of angle are known as octahedral complexes.
Types of octahedral complexes:
1) Inner d- orbital complexes:
The
orbitals in which inner d-orbital is under the process of hybridization.
Example [FeCN6]
i)
First of all, find the oxidation state of metal and charge on sphere.
CN
has O.S. = -1 and Fe has O.S. = +3. So, [Fe+3 CN6]-3
ii)
Now write the electronic configuration of iron (Fe).
Fe
= 1s2, 2s2, 2p6, 3s2, 3p6,
4s2, 3d6, 4p, 5s, 4d
iii)
Now draw electronic orbitals.
At Ground state
At excited state
iv) As CN is a
strong field ligand so it will pair up electrons. While the next six empty
orbitals will be filled up by lone pairs donated by ligands.
In above example,
the non-boning electrons do not participate in bonding. As Inner 3d orbital is
involve in bonding so the complex will be inner d orbital complex.
Hybridization is d2sp3. There will be six d2sp3
hybridized orbitals (same shape and same energy). Each orbital has a lone
pair of electron donated by CN-.
iv) The final
diagram of complex will be
v)
Usually, inner d orbitals are diamagnetic. These complexes are also known as
low spin complexes.
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2) Outer d orbital complexes
Outer
d-orbitals are paramagnetic due to free and high spins.
Example [Fe(H20)6]
Just
like above example we will find O.S. and draw electronic orbitals.
i) At Ground
state
ii) At excited
state
iii) As H2O
is a weak field ligand so it will not pair up electrons. And here again the
next six empty orbitals will be filled up by lone pairs donated by ligands. Now
in this case the hybridization will be sp3d2.
iv) Now there
will be six sp3d2 hybridized orbitals. Each orbital has a
lone pair of electron donated by H2O. The final diagram of complex will
be
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CHEMICAL KINETICS (Introduction)
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