They are extracted from their ores as ammine complexes. Magnus's green salt was one of the first examples of a metal ammine complex. Transition metal amides are intermediates in the base-induced substitution of transition metal ammine complexes. Platinum group metals form diverse ammine complexes. For example, Co complexes tend to have ammine ligands. Cisplatin (PtCl(NH)) is a coordination compound containing two chloro and two ammine ligands. Ammine complexes like hexaamminenickel chloride also exist. It is the chloride salt of the metal ammine complex [Ni(NH)]. The complex [Pt(NH)] is a rare example of a tetracationic ammine complex. It is the chloride salt of the metal ammine complex [Pt(NH)]. The complex consists of two ammine ligands and the dianion derived from glycolic acid. When the M-NH bond is weak, the ammine ligand dissociates and protonation ensues. The related metal ammine complex [Os(NH)(N)] is also known. The ammine ligands are more acidic than is ammonia (pK ~ 33). For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds.