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Ligands are classified according to the number of electrons that they "donate" to the metal. L ligands are Lewis bases. L ligands are represented by amines, phosphines, CO, N 2, and alkenes. Examples of L ligands extend to include dihydrogen and hydrocarbons that interact by agostic interactions. X ligands are halides and pseudohalides. X ...
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.
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.
Many ligands other than CO are strong "backbonders". Nitric oxide is an even stronger π-acceptor than CO and ν NO is a diagnostic tool in metal–nitrosyl chemistry. Isocyanides, RNC, are another class of ligands that are capable of π-backbonding.
For example, NO 2 − is a strong-field ligand and produces a large Δ. The octahedral ion [Fe(NO 2 ) 6 ] 3− , which has 5 d -electrons, would have the octahedral splitting diagram shown at right with all five electrons in the t 2 g level.
The nucleophilicity of hydroxo ligands is relevant to the role of some M-OH centers in enzymology. For example, in carbonic anhydrase, a zinc hydroxide binds carbon dioxide: [7] L n M−OH + CO 2 ⇌ L n MO−O−CO 2 H. The oxygen evolving complex (OEC) consists of a Mn-Ca-O-OH cluster that is responsible for the biosynthesis of O 2. It is ...
Many simple organic ligands form strong bridges between metal centers. Many common examples include organic derivatives of the above inorganic ligands (R = alkyl, aryl): OR −, SR −, NR − 2, NR 2− (imido), PR − 2 (phosphido, note the ambiguity with the preceding entry), PR 2− (phosphinidino), and many more.
Cyclopentadienyl ligands almost invariably bind to metals as ... Typical examples of this type of complex are group 14 metal ... Cobaltocene is a strong, soluble ...