Reactivity of coordinatively unsaturated iron complexes towards carbon monoxide: to bind or not to bind?

An overview of the reactivity of coordinatively unsaturated iron complexes (in most cases Fe(II)) towards carbon monoxide is presented. Unsaturated iron complexes are known with coordination numbers (CN) of two to five adopting linear or slightly bent (CN = 2), trigonal (CN = 3), tetrahedral, square...

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Bibliographic Details
Published in:Dalton transactions : an international journal of inorganic chemistry 2011-05, Vol.40 (18), p.4778-4792
Main Authors: Benito-Garagorri, David, Lagoja, Irene, Veiros, Luis F, Kirchner, Karl A
Format: Article
Language:English
Subjects:
Binding
Carbon monoxide
Charge
Coordination numbers
Field strength
Iron
Ligands
Unsaturated
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Summary:An overview of the reactivity of coordinatively unsaturated iron complexes (in most cases Fe(II)) towards carbon monoxide is presented. Unsaturated iron complexes are known with coordination numbers (CN) of two to five adopting linear or slightly bent (CN = 2), trigonal (CN = 3), tetrahedral, square planar or trigonal pyramidal (CN = 4), and square-pyramidal or trigonal-bipyramidal geometries (CN = 5), respectively. The binding of CO depends strongly on the number and the nature of co-ligands (overall ligand field strength), the charge of the complex, the complex geometry, and the spin state of the unsaturated metal center. In many cases, CO addition to high-spin iron complexes takes place with concomitant spin state changes forming compounds in the lowest possible spin state, i.e., with S = 0. In several other cases, however, the addition of CO is reversible or is even totally rejected altogether for either thermodynamic or kinetic reasons. In the case of the latter such reactions are termed "spin-blocked" or "spin forbidden".
ISSN:1477-9226
1477-9234
DOI:10.1039/c0dt01636e