Draw orbital-energy splitting diagrams and use the...

Draw orbital-energy splitting diagrams and use the spectrochemical series to show the orbital occupancy for each of the following (assuming that $\mathrm{H}_{2} \mathrm{O}$ is a weak-field ligand): (a) $\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3-}\left(\mathrm{C}_{2} \mathrm{O}_{4}^{2-} \text { creates a weaker field than } \mathrm{H}_{2} \mathrm{O} \text { does.) }\right.$ (b) $\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{4-}$ (c) $\left[\mathrm{MnCl}_{6}\right]^{4-}$

Draw orbital-energy splitting diagrams and use the spectrochemical series to show the orbital occupancy for each of the following (assuming that $\mathrm{H}_{2} \mathrm{O}$ is a weak-field ligand):
(a) $\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3-}\left(\mathrm{C}_{2} \mathrm{O}_{4}^{2-} \text { creates a weaker field than } \mathrm{H}_{2} \mathrm{O} \text { does.) }\right.$
(b) $\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{4-}$
(c) $\left[\mathrm{MnCl}_{6}\right]^{4-}$

Key Concepts

Crystal Field Theory

This is a model that describes the splitting of degenerate d orbitals in transition metal ions when they are surrounded by ligands. The approach helps in understanding the energies of the d orbitals based on their orientations relative to the ligand positions, leading to specific electronic configurations and affecting a complex’s color, magnetism, and reactivity.

Spectrochemical Series

The spectrochemical series is an empirically derived list of ligands arranged in order of the strength of the crystal field they produce. It helps predict whether a complex will be high-spin or low-spin by indicating which ligands create larger or smaller separations in d orbital energy levels.

High-spin and Low-spin Configurations

These terms refer to the arrangements of electrons in the split d orbitals of a metal ion under the influence of ligands. In high-spin complexes, electrons occupy higher energy orbitals to minimize pairing due to weaker ligand fields. In low-spin complexes, stronger ligand fields lead to pairing of electrons in lower energy orbitals, even at the cost of increased electron pairing energy.

Orbital Energy Splitting Diagrams

These diagrams visually represent the energy difference between split d orbitals in a metal ion when ligands are present. They are essential for determining how electrons fill the orbitals, which in turn explains properties like magnetism. The splitting diagram typically shows how metal orbitals separate into groups (e.g., t2g and eg in an octahedral complex) with a specific energy gap dependent on ligand field strength.

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