noun
: a compound or ion that contains a central usually metallic atom or ion combined by coordinate bonds with a definite number of surrounding ions, groups, or molecules, that retains its identity more or less even in solution, and that may be nonionic {as tri-ammine-trinitro-cobalt [Co(NH 3 ) 3 (NO 2 ) 3 ] 0 }, cationic {as hex-ammine-cobalt(III)[Co(NH 3 ) 6 ] +++ }, or anionic {as hexachloroplatinate[PtCl 6 ] -- } — see chelate I