In coordination chemistry an ammonia ligand is called an ammine. In contrast to alkyl amines it is spelled with a double "m". Cobalt(III) salts frequently actually contain hexaamminecobalt(III) (e.g. cobalt(III) hexammine chloride, [Co(NH3)6]Cl3). Tetraamminedichlorochromium(III) chloride, [Cr(NH3)4Cl2]Cl, has the unique property that the cis isomer is violet and the trans isomer is green. Tetraamminecopper(II), [Cu(NH3)4]2+, is a much deeper blue than the bare copper ion. Formation of the diamminesilver ion, [Ag(NH3)2]+, allows the generally insoluble silver chloride to dissolve in aqueous ammonia.
