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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 ...
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.
For example, the complex [Ni(dien) 2)] 2+ is more stable than the complex [Ni(en) 3)] 2+; both complexes are octahedral with six nitrogen atoms around the nickel ion, but dien (diethylenetriamine, 1,4,7-triazaheptane) is a tridentate ligand and en is bidentate. The number of chelate rings is one less than the number of donor atoms in the ligand.
In an Orgel diagram, lines with the same Russell–Saunders terms will diverge due to the non-crossing rule, but all other lines will be linear. Also, for the D Orgel diagram, the left side contains d 1 and d 6 tetrahedral and d 4 and d 9 octahedral complexes. The right side contains d 4 and d 9 tetrahedral and d 1 and d 6 octahedral complexes.
High Spin [FeBr 6] 3− crystal field diagram Conversely, ligands (like I − and Br − ) which cause a small splitting Δ of the d -orbitals are referred to as weak-field ligands. In this case, it is easier to put electrons into the higher energy set of orbitals than it is to put two into the same low-energy orbital, because two electrons in ...
Tanabe–Sugano diagrams can be used for both high spin and low spin complexes, unlike Orgel diagrams, which apply only to high spin complexes. Tanabe–Sugano diagrams can also be used to predict the size of the ligand field necessary to cause high-spin to low-spin transitions.
When a transition metal ion of configuration , = to , is in octahedral surroundings, its ground state may be low spin (LS) or high spin (HS), depending to a first approximation on the magnitude of the energy gap between and metal orbitals relative to the mean spin pairing energy (see Crystal field theory).