Synonyms: Nickelate(6-), (((1,2-ethanediylbis((nitrilo-kappaN)bis(methylene)))tetrakis(phosphonato-kappaO))(8-))-, ammonium hydrogen (1:5:1), (OC-6-21)-;Pentaammonium nickelous 1,2-ethanedi(nitrilodi(methylene phosphonate));Nickelate(6-), (((1,2-ethanediylbis((nitrilo-kappaN)bis(methylene)))tetrakis(phosphonato-kappaO))(8-))-, pentaammonium hydrogen, (OC-6-21)-;Pentaammonium hydrogen (((ethylenebis(nitrilobis(methylene)))tetrakis(phosphonato))(8-))nickelate(6-);ammonium nickel(2+) hydrogen [ethane-1,2-diylbis(nitrilodimethanediyl)]tetrakis(phosphonate) (5:1:1:1)