η

in inorganic nomenclature
synonyms: hapto, eta
https://doi.org/10.1351/goldbook.H01881
An affix giving a topological indication of the bonding between a $\ce{\uppi\!\mbox{-}electron}$ ligand and the central atom in a coordination entity. A right superscript numerical index indicates the number of ligating atoms in the $\ce{\uppi\!\mbox{-}electron}$ system of the ligand which bind to the central atom.
Examples:
  1. $\ce{[Fe(CO)3(C4H6SO)], tricarbonyl(\upeta^{2}{-}dihydrothiophene 1-oxide-\kappa O)iron}$.
  2. $\ce{[Cr(CO)4(C4H6)], tetracarbonyl(\upeta^{4}\mbox{-}2-methylene-1,3-propanediyl)chromium}$.
Source:
Red Book, 3rd ed., p. 202 [Terms]
See also:
Blue Book, p. 465 [Terms] [Book]
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1120 [Terms] [Paper]
Citation: 'η' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.H01881 RIS BibTex EndNote
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