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 \(\upeta\).
Example: \(\ce{(C5H5)2Fe}\ (\rm{ferrocene})\) = \(\ce{bis(\upeta^{5}{-}cyclopentadienyl)iron}\), where \(\upeta^{5}\) can be read as eta-five or pentahapto.