![]() This is controlled by whether Δis larger than the spin- pairing energy, P, which is the energy required to take pairs of electrons with the same spin orientation, and pair them up with the opposite spin. High and low-spin complexes: The d-electrons in d4 to d8 configurations can be high-spin, where they spread out and occupy the whole d sub-shell, or low-spin, where the t2g level is filled first. Typically, CN- produces very large values of Δ, while F- produces very small values. This energy difference is the crystal field splitting parameter Δ, also known as 10Dq, and has units of cm-1. The crystal field splitting parameter (Δ) Different ligands produce different extents of splitting between the eg and the t2g levels. Splitting of the d sub-shell in an octahedral complex energy eg d-shell split by presence of ligand donor-atoms Δ 3d sub-shell Co3+ ion in gas-phase (d6) t2g Co(III) in octahedral complex Splitting of the d sub-shell in octahedral coordination blue = ligand donor atom orbitals theegset thet2g set z z z y y y x x x dyz dz2 dx2-y2 the two orbitals of the eg set lie along the Cartesian coordinates, and so are adjacent to the donor atoms of the ligands, which raises the egset in energy the three orbitals of thet2g set lie between the ligand donor-atoms (only dyz shown) The d-orbitals: thet2g set z z z y y y x x x dyz dxy dxz z z y y theeg set x x dz2 dx2-y2 ![]() eg energy d-shell split by presence of ligand donor-atoms Δ 3d sub-shell Co3+ ion in gas-phase (d6) t2g Co(III) in complex Bonding in complexes of d-block metal ions – Crystal Field Theory.
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