κ (kappa)

in inorganic nomenclature
https://doi.org/10.1351/goldbook.K03366
An affix in the name of a polydentate chelate complex indicating single ligating atom attachments of a polyatomic ligand to a coordination centre. A right superscript numerical index indicates the number of such attachments. Example: Ni[(CH3)2PCH2CH2P(CH3)2]Br2, dibromobis[1,2-ethanediylbis(dimethylphosphine)-κ2P]nickel(II).
Source:
Red Book,3rd ed., p. 174 (https://doi.org/10.1515/pac-2014-0718)