Metallate or metalate is the name given to any complex anion containing a metal ligated to two or more atoms and/or groups of atoms.
Typically, the metal is one of the transition elements and the ligand is oxygen or another chalcogenide, a cyanide group or a halogen (though others are known).
The chalcogenide metallates are known as oxometallates, thiometallates, selenometallates and tellurometallates; the cyanide metallates are known as cyanometallates; the halogenide metalates are known as halogenometallates.
Oxometallates include permanganate MnO−4, chromate CrO2−4, vanadate VO−3 or VO3−4 and tungstate WO2−4.
Thiometallates include tetrathiovanadate VS3−4, tetrathiomolybdate MoS2−4, tetrathiotungstate WS2−4and similar ions. [1]
Cyanometallates include ferricyanide [Fe(CN)6]3−, ferrocyanide [Fe(CN)6]4− and dicyanoargentate(I) [Ag(CN)2]−.
Halogenometallates include tetrachloroaluminate [AlCl4]−, tetrachloronickelate(II) [NiCl4]2− and hexafluoroplatinate(V) [PtCl6]−.
Others include tetranitratoaluminate [Al(NO3)4]− and tetrahydroxozincate [Zn(OH)4]2−.
Metallate is also used as a verb by bioinorganic chemistry to describe the act of adding metal atoms or ions to a site (synthetic ligand or protein).
