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Representative d-orbital splitting diagrams for square planar complexes featuring σ-donor (left) and σ+π-donor (right) ligands. A general d-orbital splitting diagram for square planar (D 4h) transition metal complexes can be derived from the general octahedral (O h) splitting diagram, in which the d z 2 and the d x 2 −y 2 orbitals are degenerate and higher in energy than the degenerate ...
Square planar and other complex geometries can also be described by CFT. The size of the gap Δ between the two or more sets of orbitals depends on several factors, including the ligands and geometry of the complex. Some ligands always produce a small value of Δ, while others always give a large splitting.
Complexes have been described for all of the transition metals. [citation needed] Although few have any practical value, these complexes have been influential. [1] 2,2'-Bipyridine (bipy) is classified as a diimine ligand. Unlike the structures of pyridine complexes, the two rings in bipy are coplanar, which facilitates electron delocalization ...
Examples of associative mechanisms are commonly found in the chemistry of 16e square planar metal complexes, e.g. Vaska's complex and tetrachloroplatinate. These compounds (MX 4) bind the incoming (substituting) ligand Y to form pentacoordinate intermediates MX 4 Y that in a subsequent step dissociates one of their ligands.
The derivations used in octahedral geometry are valid for most other geometries. The exception is square-planar because square-planar complexes typically abide by the 16-electron rule. Assuming ligands act as two-electron donors the metal center in square-planar molecules is d 8.
Complexes with the 2:1 stoichiometry are illustrated by copper(II) glycinate [Cu(O 2 CC(R)HNH 2) 2], which exists both in anhydrous and pentacoordinate geometries. When the metal is square planar, these complexes can exist as cis and trans isomers. The stereochemical possibilities increase when the amino acid ligands are not homochiral ...
With species such as the square-planar complex of the silver(II) ion [AgF 4] 2− the relevant double group is also D 4 ′; deviations from the spin-only value are greater as the magnitude of spin–orbit coupling is greater for silver(II) than for copper(II). [40] A double group is also used for some compounds of titanium in the +3 oxidation ...
The complexes used to assemble cavitand cages are square planar with one η2 ligand; this helps enforce the final geometry. Without cis geometry, only small oligomers will form. Self-assembly also requires a ligand exchange; weakly bound ions such as BF 4 - and PF 6 - promote assembly because they leave the complex so it can bind with the ...