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Spin crossover (SCO) is a phenomenon that occurs in some metal complexes wherein the spin state of the complex changes due to an external stimulus. The stimuli can include temperature or pressure. [1] Spin crossover is sometimes referred to as spin transition or spin equilibrium behavior. The change in spin state usually involves interchange of ...
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. There are two Orgel diagrams, one for d 1, d 4, d 6, and d 9 configurations and the other with d 2, d 3, d 7, and d 8 configurations.
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 ...
Low-spin [Fe(NO 2) 6] 3− crystal field diagram. The Δ splitting of the d orbitals plays an important role in the electron spin state of a coordination complex. Three factors affect Δ: the period (row in periodic table) of the metal ion, the charge of the metal ion, and the field strength of the complex's ligands as described by the spectrochemical series.
There is no electron repulsion in a d 1 complex, and the single electron resides in the t 2g orbital ground state. A d 1 octahedral metal complex, such as [Ti(H 2 O) 6] 3+, shows a single absorption band in a UV-vis experiment. [7] The term symbol for d 1 is 2 D, which splits into the 2 T 2g and 2 E g states.
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.
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.
Iron(III) acetylacetonate, Fe(acac) 3, is a red high-spin complex that is highly soluble in organic solvents. It is a high-spin complex with five unpaired electrons. It has occasionally been investigated as a catalyst precursor. [18] Fe(acac) 3 has been partially resolved into its Δ and Λ isomers. [19] The ferrous complex Fe(acac) 2 is ...