hapticity 

https://doi.org/10.1351/goldbook.08174
Topological description for the number of contiguous atoms of a ligand that are bonded to a central metal atom.
Note:
The hapticity is indicated as a superscript following the Greek letter η.
Example:
(CA5HA5)A2Fe (ferrocene) = bis(ηA5-cyclopentadienyl)iron, where η5 can be read as eta-five or pentahapto.
Source:
PAC, 2022, 94, 353. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)) on page 429 [Terms] [Paper]
Citation: 'hapticity' 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.08174 RIS BibTex EndNote
Div. IIITextXMLJSON