Download Transition metal compounds have interesting magnetic properties.

Transition metal compounds have
interesting magnetic properties.
Diamagnetic
Paramagnetic
Ferromagnetic
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The magnetic properties of a complex depends on the
number of unpaired electrons
Na+
Mn2+
Ti2+
Co3+
Experiment shows:
[Co(CN)6]3– has no unpaired electrons
[CoF6]3– has four unpaired electrons
WHY do they have different numbers of unpaired electrons?
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CRYSTAL FIELD THEORY can be used to explain this result.
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M in spherical Oh Field
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d orbitals in uniform,
“spherical” field of negative
charge; all orbitals raised in
energy equally
d orbitals in free
metal ion (all
degenerate)"
Presence of ligand electrons raises energy of metal d orbitals due
to electrostatic repulsion
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The octahedral ligand field (or crystal field) causes
the d orbitals to split into two energy levels."
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e! config
# unpaired e!
P = spin pairing energy
= energy needed to pair electrons in the same orbital.
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For an ion with a d4 electron configuration the number of
unpaired electrons will depend on ".
Which one will be high spin (more unpaired e!)?
Low spin (fewer unpaired e!)?
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The magnitude of " (=Crystal field splitting energy)
influences the properties of metal complexes.
How big is " ?
How does " affect properties of complexes?
The magnitude of " depends on:
1. 
2. 
3. 
4. 
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OCTAHEDRAL COMPLEXES"
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Which of the diagrams below corresponds to [CoF6]3– and which
corresponds to [Co(CN)6]3–?
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WHY?"
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What properties of these complexes would be different?""
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"@/>/=C):G)L)=:)/36740A4)=<4)43472C)20F"
Cl! < F! < H2O < NH3 < en < NO2! < CN!
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Increasing"! "
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The color of a complex depends on:
1. The element
2. Its oxidation state
3. Identity of ligands
Example:
V(H2O)63+
green
V(H2O)62+
violet
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When light of a
certain wavelength is
absorbed by a
complex, the complex
will appear the
complementary color
of the wavelength
absorbed (you see
the light that is
REFLECTED!)
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How do we explain the colors of metal complexes?
Visible absorption spectrum of [Ti(H2O)6]3+ : what color is it?
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Ni2+ (aq)
[Ni(H2O)6]2+ + 6 NH3 h [Ni(NH3)6]3+ + 6 H2O
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The observed color is related to the amount of
energy required to promote an electron.
Compare " to energy absorbed.
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Which of these complexes absorbs
light at the shorter wavelength?
Which complex has the larger !o?"
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