GOVERNMENT ENGINEERING COLLEGE KONI,
BILASPUR, C.G.
SESSION – 2022-2023
BACHELOR OF TECHNOLOGY (MECHANICAL)
DEPARTMENT OF CHEMISTRY
PRESENTATION
CHEMISTRY.
GUIDED BY
PROF. NAVIN KUMAR VERMA
Roll No. - 300703722035
PRESENTATION BY
Arya Meher
2ND Sem. Mechanical
1
CRYSTAL FIELD THEORY
Crystal field theory (CFT) describes the breaking of orbital degeneracy in transition metal
complexes due to the presence of ligands. CFT qualitatively describes the strength of the
metal-ligand bonds.
Crystal field theory was proposed which described the metal-ligand
bond as an ionic bond arising purely from the electrostatic
interactions between the metal ions and ligands. Crystal field theory
considers anions as point charges and neutral molecules as dipoles.
When transition metals are not bonded to any ligand, their d orbitals
degenerate that is they have the same energy. When they start bonding
with other ligands, due to different symmetries of the d orbitals and
the inductive effect of the ligands on the electrons, the d orbitals
split apart and become non-degenerate.
GROUPING AND
ALLIGNMENT OF D
ORBITALS
-
Eg SET
Have lobes along
axes.
Also called axial
orbitals.
Letter ‘e’ refers to
doubly degenerate
set
-
t2g set
Have lobes lying
between the axes.
Also called non
axial orbitals.
Letter ‘t’ refers to
Triply degenerate
set.
- All the d orbitals on the
metal have same energy in
free atom while during
complex formation the ligand
destroy degeneracy of these
orbitals.
GROUPING AND
ALLIGNMENT OF D
ORBITALS
-
Eg SET
Have lobes along
axes.
Also called axial
orbitals.
Letter ‘e’ refers to
doubly degenerate
set
-
t2g set
Have lobes lying
between the axes.
Also called non
axial orbitals.
Letter ‘t’ refers to
Triply degenerate
set.
- All the d orbitals on the
metal have same energy in
free atom while during
complex formation the ligand
destroy degeneracy of these
orbitals.
GROUPING AND
ALLIGNMENT OF D
ORBITALS
-
Eg SET
Have lobes along
axes.
Also called axial
orbitals.
Letter ‘e’ refers to
doubly degenerate
set
-
t2g set
Have lobes lying
between the axes.
Also called non
axial orbitals.
Letter ‘t’ refers to
Triply degenerate
set.
- All the d orbitals on the
metal have same energy in
free atom while during
complex formation the ligand
destroy degeneracy of these
orbitals.
CRYSTAL FIELD
SPLITTING IN
OCTAHEDRAL
COMPLEX
In an octahedral complex, there are six ligands attached to the central transition metal. The d-orbital splits
into two different levels. The bottom three energy levels are named dxy, dxz, and dyz (collectively referred to
as t2g). The two upper energy levels are named dx2−y2, and dz2 (collectively referred to as eg).
The reason they split is because of the electrostatic interaction between the electrons of the ligand and the
lobes of the d-orbital. In an octahedral, the electrons are attracted to the axes. Any orbital that has a lobe on
the axes moves to a higher energy level. This means that in an octahedral, the energy levels of eg are higher
(0.6∆o) while t2g is lower (0.4∆o).
CRYSTAL FIELD
SPLITTING IN
TETRAHEDRAL
COMPLEX
In a tetrahedral complex, there are four ligands attached to the central metal. The d orbitals also
split into two different energy levels. The top three consist of the dxy, dxz, and dyz orbitals. The
bottom two consist of the dx2−y2 and dz2 orbitals. The reason for this is due to poor orbital overlap
between the metal and the ligand orbitals. The orbitals are directed on the axes, while the ligands
are not.
CALCULATING CFSE
AND MAGNETIC
PROPERTY
1. Determine nature of
ligand and complex.
2. Calculate the
oxidation state of
metal ion.
3. Write down the
electronic configuration.
4. Fill the electrons in
the non degenerate
orbitals considering the
nature of complex.
[Fe(Cl)6]3-
Now by formula. –
- For octahedral complex =
[x(0.6) – y(0.4)] ΔO
Now by formula. –
- For tetrahedral complex =
[-x(0.6) + y(0.4)] ΔO
- Where x and y are no. of electrons in eg
and t2g set.
CALCULATING CFSE
AND MAGNETIC
PROPERTY
1. Determine nature of
ligand and complex.
2. Calculate the
oxidation state of
metal ion.
[Fe(Cl)6]3-
3. Write down the
electronic configuration.
4. Fill the electrons in
the non degenerate
orbitals considering the
nature of complex.
Nature of ligand – Weak field
Nature of complex – octahedral high spin
Oxidation state of Fe – 3+
Now by formula. –
- For octahedral complex =
[x(0.6) – y(0.4)] ΔO
Now by formula. –
- For tetrahedral complex =
[-x(0.6) + y(0.4)] ΔO
- Where x and y are no. of electrons in eg
and t2g set.
CALCULATING CFSE
AND MAGNETIC
PROPERTY
1. Determine nature of
ligand and complex.
2. Calculate the
oxidation state of
metal ion.
[Fe(Cl)6]3-
3. Write down the
electronic configuration.
4. Fill the electrons in
the non degenerate
orbitals considering the
nature of complex.
Electronic configuration of Fe 3+ = [Ar], 3d5
Now by formula. –
- For octahedral complex =
[x(0.6) – y(0.4)] ΔO
Now by formula. –
- For tetrahedral complex =
[-x(0.6) + y(0.4)] ΔO
- Where x and y are no. of electrons in eg
and t2g set.
CALCULATING CFSE
AND MAGNETIC
PROPERTY
1. Determine nature of
ligand and complex.
2. Calculate the
oxidation state of
metal ion.
3. Write down the
electronic configuration.
4. Fill the electrons in
the non degenerate
orbitals considering the
nature of complex.
[Fe(Cl)6]3-
2 x 0.6 – 3 x 0.4 = 0ΔO
Now by formula. –
- For octahedral complex =
[x(0.6) – y(0.4)] ΔO
Now by formula. –
- For tetrahedral complex =
[-x(0.6) + y(0.4)] ΔO
- Where x and y are no. of electrons in eg
and t2g set.
THANK YOU