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The magnitude of Δ o is determined by the field-strength of the ligand: strong field ligands, by definition, increase Δ o more than weak field ligands. Ligands can now be sorted according to the magnitude of Δ o (see the table below). This ordering of ligands is almost invariable for all metal ions and is called spectrochemical series.
A spectrochemical series is a list of ligands ordered by ligand "strength", and a list of metal ions based on oxidation number, group and element.For a metal ion, the ligands modify the difference in energy Δ between the d orbitals, called the ligand-field splitting parameter in ligand field theory, or the crystal-field splitting parameter in crystal field theory.
In inorganic chemistry, the cis effect is defined as the labilization (or destabilization) of CO ligands that are cis to other ligands. CO is a well-known strong pi-accepting ligand in organometallic chemistry that will labilize in the cis position when adjacent to ligands due to steric and electronic effects.
As described above, π-donor ligands lead to a small Δ O and are called weak- or low-field ligands, whereas π-acceptor ligands lead to a large value of Δ O and are called strong- or high-field ligands. Ligands that are neither π-donor nor π-acceptor give a value of Δ O somewhere in-between.
The use of hemilabile ligands allows structural motifs synthesized via the WLA to be modified with small molecule effectors much like allosteric enzymes in biology. As described above, the weak Y–M bond can be easily displaced by a coordinating ligands including Cl −, CO, CH 3 CN, RCO 2 −, and a variety of nitriles/isonitriles (Figure 2).
In other projects Wikidata item ... isothiocyanate is a weak-field ligand. Two examples are the ... and isothiocyanate ligands. Examples are found for heavy ...
In contrast to O-bonded phosphine oxide ligands, the P-bonded phosphine oxides are strong field ligands. These ligands, which tend to engage in intramolecular hydrogen bonds. Illustrative is the complex derived from dimethylphosphine oxide , PtH(PMe 2 OH) 2 (PMe 2 O) (Me = CH 3 ).
Halides are X-type ligands in coordination chemistry. They are both σ- and π-donors. Chloride is commonly found as both a terminal ligand and a bridging ligand. The halide ligands are weak field ligands. Due to a smaller crystal field splitting energy, the homoleptic halide complexes of the first transition series are all high spin.