Tetraiodonickelate(II) is a complex ion of nickel with four iodide 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 or methanol can partition [NiI4]2− ions into a cyclohexane-amine mixture. The solution formed is blood red.[3]
History
Already in 1909 Cambi had noticed that a mixture of nickel iodide and sodium iodide dissolved in acetone has a red colour. This red colour was due to the presence of tetraiodonickelate.[1]
Salts
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 a molecular weight of 826.8135 and a CAS number of 13927-28-1.[5]
1,2,6-Trimethylpyrazinium tetraiodonickelate has CAS 88227-96-7.[citation needed]
References
^ abcdeGill, Naida S.; Nyholm, R. S. (1959). "802. Complex halides of the transition metals. Part I. Tetrahedral nickel complexes". Journal of the Chemical Society (Resumed): 3997. doi:10.1039/JR9590003997.
^Hollebone, B. R. (1971). "Pseudo-halide complexes of transition metals. Part II. Spectra, structure, and nature of bonding". Journal of the Chemical Society A: Inorganic, Physical, Theoretical: 484. doi:10.1039/J19710000481.
^Florence, T. M.; Farrar, Yvonne J. (July 1968). "Liquid-liquid extraction of nickel with long-chain amines from aqueous and nonaqueous halide media". Analytical Chemistry. 40 (8): 1200–1206. doi:10.1021/ac60264a010.