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Generally, the rates of ligand dissociation from low spin complexes are lower than dissociation rates from high spin complexes. In the case of octahedral complexes, electrons in the e g levels are anti-bonding with respect to the metal-ligand bonds. Famous "exchange inert" complexes are octahedral complexes of d 3 and low-spin d 6 metal ions ...
In an octahedral complex, the molecular orbitals created by coordination can be seen as resulting from the donation of two electrons by each of six σ-donor ligands to the d-orbitals on the metal. In octahedral complexes, ligands approach along the x -, y - and z -axes, so their σ-symmetry orbitals form bonding and anti-bonding combinations ...
Spin crossover is sometimes referred to as spin transition or spin equilibrium behavior. The change in spin state usually involves interchange of low spin (LS) and high spin (HS) configuration. [2] Spin crossover is commonly observed with first row transition metal complexes with a d 4 through d 7 electron configuration in an octahedral ligand ...
Orgel diagrams will, however, show the number of spin allowed transitions, along with their respective symmetry designations. In an Orgel diagram, the parent term (P, D, or F) in the presence of no ligand field is located in the center of the diagram, with the terms due to that electronic configuration in a ligand field at each side.
Octahedral high spin: 3 unpaired electrons, paramagnetic, substitutionally labile. Octahedral low spin: 1 unpaired electron, paramagnetic, substitutionally labile. Examples: cobaltocene. d 8 Complexes which are d 8 high-spin are usually octahedral (or tetrahedral) while low-spin d 8 complexes are generally 16-electron square planar complexes.
Due to a smaller crystal field splitting energy, the homoleptic halide complexes of the first transition series are all high spin. Only [CrCl 6] 3− is exchange inert. Homoleptic metal halide complexes are known with several stoichiometries, but the main ones are the hexahalometallates and the tetrahalometallates.
As noted above, e g refers to the d z 2 and d x 2-y 2 which are higher in energy than the t 2g in octahedral complexes. If the energy required to pair two electrons is greater than Δ, the energy cost of placing an electron in an e g, high spin splitting occurs.
Fe(acac) 3 is an octahedral complex with six equivalent Fe-O bonds with bond distances of about 2.00 Å. The regular geometry is consistent with a high-spin Fe 3+ core with sp3d2 hybridization. As the metal orbitals are all evenly occupied the complex is not subject to Jahn-Teller distortions and thus adopts a D 3 molecular symmetry.