The difference
in energy of eg and t2g Orbitals are called crystal
field stabilisation energy (CFSE):
Calculation shows that coordination entities with four to seven d electron are more stable for strong field as compared to weak field cases.
Where m and n = are number of electrons
in t2g and eg orbitals
respectively and del.oct is crystal field splitting energy in octahedral Complexes.
l = represents the
number of extra electron pair formed because of the ligands in comparison to
normal degenerate configuration.
P= (Pairing energy) the energy required for electron pairing in a single orbital. The actual configuration of complex adopted is decided by the relative values of delta and P
Case (1): If del.oct is less than P :
We have so called weak field or high spin situation, the fourth electron entered one of the eg orbitals giving configuration (t2g3 and eg1)
If now 5th electron is added to a weak field the configuration become (t2g3 and eg2).
Case (2): If del.oct is more than P: we have the strong field , low spin situation and pairing will occur in the t2g level with eg level remaining unoccupied in entities of d1 and d6 ions .
P= (Pairing energy) the energy required for electron pairing in a single orbital. The actual configuration of complex adopted is decided by the relative values of delta and P
Case (1): If del.oct is less than P :
We have so called weak field or high spin situation, the fourth electron entered one of the eg orbitals giving configuration (t2g3 and eg1)
If now 5th electron is added to a weak field the configuration become (t2g3 and eg2).
Case (2): If del.oct is more than P: we have the strong field , low spin situation and pairing will occur in the t2g level with eg level remaining unoccupied in entities of d1 and d6 ions .
Calculation shows that coordination entities with four to seven d electron are more stable for strong field as compared to weak field cases.
(A)For
configuration (d0, d1, d2, d3, d8,
d9, d10):
|
SN
|
METAL ION
|
EXAMPLE
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CONF IN L.F
|
CFSE(del.oct)
|
|
1
|
d0
|
Sc3+
|
t2g 0,0,0 eg 0
|
=0.0
|
|
2
|
d1
|
Ti3+
|
t2g 1,0,0 eg 0
|
=-0.4
|
|
3
|
d2
|
V3+
|
t2g 1,1,0 eg 0
|
=-0.8
|
|
4
|
d3
|
Cr3+ , V2+
|
t2g1,1,1 eg 0
|
=-1.2
|
|
5
|
d8
|
Ni2+
|
t2g 2,2,2 eg1,1
|
= -2.4 +1.2+ 3P
=-1.2+3P
|
|
6
|
d9
|
Cu2+
|
t2g2,2,2 eg
2,1
|
=-2.4 +1.8+4P
=-0.6+ 4P
|
|
7
|
d10
|
Zn2+
|
t2g2,2,2 eg
2,2
|
=-2.4 +2.4+ 5P
= 5P
|
Therefore,
for the above configurations, there is no effect of the nature of ligand. They may be strong
or weak; the formula for CFSE will remain the same.
(A)For configuration (d4, d5, d6, d7):
|
SN
|
METAL ION
|
EXAMPLE
|
CONF IN L.F
|
CFSE(del.oct)
|
|
1
|
d4
|
Cr2+ (S.L.)
Cr2+ (W.L.)
|
t2g 2,1,1 eg
0,0
t2g 1,1,1 eg
1,0
|
=-1.6 +1P
=-1.6
|
|
2
|
d5
|
Mn2+,Fe3+(S.L.)
(W.L)
|
t2g 2,2,1 eg
0,0
t2g 1,1,1 eg
1,1
|
=-2.0+2P
=0.0
|
|
3
|
d6
|
Co3+,Fe2+(S.L.)
(W.L.)
|
t2g 2,2,2 eg 0,0
t2g 2,1,1 eg 1,1
|
=-2.4 +3P
=-0.4+ 1P
|
|
4
|
d7
|
Co2+ (S.L.)
(W.L.)
|
t2g2,2,2 eg 1,0
t2g2,2,1 eg
1,1
|
=-1.8+3 P
-0.8+2P
|
Crystal field stabilisation energy (CFSE) in Tetrahedral:
The difference in energy of eg and t2g
Orbitals are called crystal field stabilisation energy
(CFSE) in tetrahedral complexes:
Where m
and n = are
number of electrons in t2g
and eg orbitals
respectively and del.oct
is crystal field splitting energy in octahedral Complexes.
l = represents the number of extra electron pair formed because of the ligands in comparison to normal degenerate configuration.
P= (Pairing energy) the energy required for electron pairing in a single orbital. The actual configuration of complex adopted is decided by the relative values of delta and P
l = represents the number of extra electron pair formed because of the ligands in comparison to normal degenerate configuration.
P= (Pairing energy) the energy required for electron pairing in a single orbital. The actual configuration of complex adopted is decided by the relative values of delta and P
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