Tetraiodonickelate(II) is a complex ion ofnickel with fouriodide ions [NiI4]2− arranged in a tetrahedron.[1] [NiI4]2− is red in solution. This colour is due to absorption around 530 nm and below 450 nm. Maximum light transmission is around 620 nm, which is red. A broad weak absorption in the near infrared is at 740 nm.[1] The magnetic moment is anomalously low.[2]
A mixture of lithium iodide and nickel iodide in water ormethanol can partition [NiI4]2− ions into acyclohexane-amine mixture. The solution formed is blood red.[3]
Already in 1909 Cambi had noticed that a mixture ofnickel iodide andsodium iodide dissolved in acetone has a red colour. This red colour was due to the presence of tetraiodonickelate.[1]
Bis(triphenylmethylarsonium) tetraiodoronickelate [(C6H5)3CH3As]2[NiI4][4] is red in colour.[1] It can be made from triphenylmethylarsonium iodide and nickel iodide in hot ethanol. The red flakes that precipitate must be filtered before the alcohol cools, else the compound decomposes.[1]
Bis(tetraethylammonium) tetraiodonickelate [(C2H5)4N]2[NiI4] has amolecular weight of 826.8135 and a CAS number of 13927-28-1.[5]