Crystal Field Theory (CFT) describes the breaking of degeneracies of electronic orbitals in transition metal complexes due to the presence of ligands. It explains how the arrangement of ligands around a central metal ion affects the energy levels and properties like color and magnetism.
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In an octahedral field, $d$-orbitals split into two sets: $e_g$ (higher energy) and $t_{2g}$ (lower energy).
The difference in energy between these sets is called the crystal field splitting energy ($\Delta_0$).
Strong-field ligands cause larger splitting ($\Delta_0$), often leading to low-spin complexes, whereas weak-field ligands cause smaller splitting, often resulting in high-spin complexes.
According to CFT, the color of coordination compounds arises from electronic transitions between split $d$-orbitals.
Magnetic properties of coordination compounds can be predicted by examining unpaired electrons in these split orbitals.
Review Questions
What causes the splitting of $d$-orbitals in Crystal Field Theory?
How does the strength of a ligand affect the spin state of a complex?
Why do coordination compounds exhibit different colors according to CFT?
An extension of Crystal Field Theory that incorporates molecular orbital theory to better explain bonding in coordination compounds.
$d$-Orbital Splitting: The division of degenerate $d$-orbitals into groups with different energies due to ligand interactions in a coordination compound.
A coordination complex where electrons occupy higher-energy orbitals first, resulting in more unpaired electrons due to smaller crystal field splitting.