Tetraiodonickelate

Tetraiodonickelate is a complex ion of nickel with four iodide atoms [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 NiI42− 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]2NiI4 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 has a molecular weight of 826.8135 and a CAS number of 13927-28-1.[4]

1,2,6-trimethyl-pyrazinium-tetraiodonickelate has CAS 88227-96-7.

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References
  1. Gill, 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.
  2. 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.
  3. 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.
  4. "bis(tetraethylammonium) tetraiodonickelate". webbook.nist.gov. Retrieved 14 June 2016.
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