Tetrachloronickelate

A tetrahedral tetrachloronickelate complex ion

Tetrachloronickelates are a class of chemical compounds containing anions consisting of a nickel atom surrounded by four chloride ions.

room temperature tetrachloronickelate complex in water

Substituted ammonia tetrachloronickelates can be thermochromic. At room temperature they can be in a polymeric yellow coloured form, but when heated become bright blue, as the form changes to a tetrahedral arrangement of chlorine around the nickel atom.[1] Yet other amine salts of tetrachloronickelate, such as [(NC3H7)3NH]2NiCl4, are blue liquids at room temperature.[1] The trimethylammonium and diethylammonium salts have thermochromic temperatures at 70 °C. The corresponding tetrabromonickelates are also thermochromic with a transition at lower temperatures.[1]

Some tetrachloronickelates can be ionic liquids at room temperature.

formula name Ni Ox structure Remarks references
[C2mim]2NiCl4 1-ethyl-3-methylimidazolium tetrachloronickelate(II) 2 tetragonal I41/a a=14.112 c=19.436 V=3871.1 Z=8 density=1.47 MW=422.84 melt 92° [2][3]
[C4mim]2NiCl4 1-butyl-3-methylimidazolium tetrachloronickelate(II) 2 dark blue melt 56° [2]
[C5mim]2NiCl4 1-pentyl-3-methylimidazolium tetrachloronickelate(II) 2 dark blue liquid [2]
[C6mim]2NiCl4 1-hexyl-3-methylimidazolium tetrachloronickelate(II) 2 dark blue liquid [2]
[C7mim]2NiCl4 1-heptyl-3-methylimidazolium tetrachloronickelate(II) 2 dark blue liquid [2]
[C8mim]2NiCl4 1-octyl-3-methylimidazolium tetrachloronickelate(II) 2 dark blue liquid [2]

References

  1. 1 2 3 Ferraro, John R.; Sheren, Anne T. (3 February 1978). "Some new thermochromic complexes of Nickel(II) of the type [R/sub x/NH/sub 4-x/]2NiCl4". Inorganic Chemistry 17 (9): 2798–2502. doi:10.1021/ic50187a032.
  2. 1 2 3 4 5 6 Meredith, M. Brett; McMillen, C. Heather; Goodman, Jonathan T.; Hanusa, Timothy P. (August 2009). "Ambient temperature imidazolium-based ionic liquids with tetrachloronickelate(II) anions". Polyhedron 28 (12): 2355–2358. doi:10.1016/j.poly.2009.04.037.
  3. ↑ Hitchcock, Peter B.; Seddon, Kenneth R.; Welton, Thomas (1993). "Hydrogen-bond acceptor abilities of tetrachlorometalate(II) complexes in ionic liquids". Journal of the Chemical Society, Dalton Transactions (17): 2639. doi:10.1039/DT9930002639.
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