The bonding in lanthanide complexes differs from that seen in transition metal complexes. Discuss how this difference in bonding explains why for a transition metal ion, such as Co3+, the colour of its complexes varies depending on the co-ordinated ligands, whilst all complexes of a particular lanthanide ion, such as Eu3+, exhibit a similar colour (b) Solution Lanthanides (inner transition metals) resemble 3d transition metals mainly in forming coloured complexes. But they differ in the oxidation state which is due to large reduction potential for oxidation state when related to 1 electron reduction in case transition compounds. There is a lack in 4f chemistry of very high oxidation state is familiar to 3d transition complexes. The 4f metals are not willing to form strong Ln = O double bond complexes and lack of significant third ionization energy IE 3 is important in maintaining +3 oxidation state at the end of the lanthanide series. The increase in atomic radius is greater than between 3d and 4d metals than between the 4d and 5d metals because of lanthanide contraction. Sigma bonding interaction in coordination compound is due to attraction of electrons on the ligand for the charge of metal ion. Electrons in ligands repel electrons in unhybridised d orbital of metal ion. The transition metal ion like Co +3 complexes exhibit many intense colours in host crystals or solutions. The colour of light absorbed by complexed ion is related to electronic energy changes in structure of complex. The electron leaping from a lower energy state to a higer energy state. If the crystal field strength is weak and the energy gap is small leading to unpaired electrons and form a paramagnetic complex in case of 4th and 5th electron going to higher energy d z 2 and d x 2 - d y 2 . The fourth through 6 electrons will pair with d xy , d yz , and d zx . if the field is strong and the energy gap is large, leading to paired electrons and a diamagnetic complex The colour of transition metal ion, Co +3 complexes differs depends on the coordinated ligands, which is due to change in electronic energy in the structure of complex while colour of particular lanthainde Eu 3+ (europium) exhibit similar pale pink clour this is due to f-->f transition rather than d--->d transition. .

1. The bonding in lanthanide complexes differs from that seen in transition metal complexes.
Discuss how this difference in bonding explains why for a transition metal ion, such as Co3+, the
colour of its complexes varies depending on the co-ordinated ligands, whilst all complexes of a
particular lanthanide ion, such as Eu3+, exhibit a similar colour (b)
Solution
Lanthanides (inner transition metals) resemble 3d transition metals mainly in forming coloured
complexes.
But they differ in the oxidation state which is due to large reduction potential for oxidation state
when related to 1 electron reduction in case transition compounds.
There is a lack in 4f chemistry of very high oxidation state is familiar to 3d transition complexes.
The 4f metals are not willing to form strong Ln = O double bond complexes and lack of
significant third ionization energy IE 3 is important in maintaining +3 oxidation state at the end
of the lanthanide series.
The increase in atomic radius is greater than between 3d and 4d metals than between the 4d and
5d metals because of lanthanide contraction.
Sigma bonding interaction in coordination compound is due to attraction of electrons on the
ligand for the charge of metal ion.
Electrons in ligands repel electrons in unhybridised d orbital of metal ion. The transition metal
ion like Co +3
complexes exhibit many intense colours in host crystals or solutions.
The colour of light absorbed by complexed ion is related to electronic energy changes in
structure of complex.
The electron leaping from a lower energy state to a higer energy state. If the crystal field strength
is weak and the energy gap is small leading to unpaired electrons and form a paramagnetic
complex in case of 4th and 5th electron going to higher energy d z
2
and d x
2
- d y
2
.
The fourth through 6 electrons will pair with d xy , d yz , and d zx . if the field is strong and the
energy gap is large, leading to paired electrons and a diamagnetic complex

2. The colour of transition metal ion, Co +3
complexes differs depends on the coordinated ligands,
which is due to change in electronic energy in the structure of complex while colour of particular
lanthainde Eu 3+
(europium) exhibit similar pale pink clour this is due to f-->f transition rather
than d--->d transition.