21.4 Crystal Field Theory

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    Review of Electron Configurations for Transition Metals

    For transition metal cations, remember to remove the ‘s’ electrons before the ‘d’ in the valence shell.
    Remember the exceptions of Cr ([Ar]4s13d5) group and Cu ([Ar]4s13d10) group.

    Give the noble gas electronic configurations for the following:

    Sc3+

    Cr3+

    Fe3+

    Cu+

    Mn2+

    Crystal Field Splitting Energy (CFSE or Δ or Δq)

    crystal field splitting energy 01
    Coordination
    Number
    Geometry Hybridization
    2 Linear sp
    4 Tetrahedral sp3
    4 Square Planar dsp3
    6 Octahedral d2sp3 / sp3d2

    Octahedral Complexes

    Ligands in an octahedral complex reside on the axes and so the two orbitals mostly on the axes end up higher in energy.

    octahedral splitting 01
    OCTAHEDRAL COMPLEXES
    High Spin

    Each of the 5 orbitals gets an
    electron before pairing them up
    Low Spin

    The 3 lower energy orbitals are filled
    before placing an e- in a higher orbital
    Weak Field

    Describes a ligand causing a small
    Δq resulting in a high spin complex
    Strong Field

    Describes a ligand causing a large Δq
    resulting in a low spin complex

    -An octahedral complex must have 4-7 d electrons to form distinct low and high spin complexes.

    Tetrahedral Complexes

    -Always High Spin (small Δq)

    tetrahedral splitting 01

    Square Planar Complexes

    -Only occur for d8 transition metals

    square planar splitting 01