Tetrabromonickelate

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The tetrabromonickelate anion contains a doubly-charged nickel atom (Ni2+) surrounded by four

tetrahedral
arrangement. The formula is [NiBr4]2−.

The anion combines with cations to form a series of salts called tetrabromonickelates. Strongly-coordinating solvents will displace one or more of the bromido ligands from the complex.[1] Solvents that can dissolve tetrabromonickelate include

methyl ethyl ketone, and nitromethane.[2]

In the

near infrared called ν2 near 770 nm is due to the 3T1(F) → 3A2(F) transition.[2]

Salts

Dilithium tetrabromonickelate forms a dark blue solution in tetrahydrofuran.[3]

A mixture of lithium bromide and nickel bromide in water or methanol can transfer [NiBr4]2− ions into a cyclohexane-amine mixture. The solution formed is green.[4]

Tetraethylammonium tetrabromonickelate is blue.[5][6]

tetra-n-butylammonium tetrabromonickelate is purple blue in color, melting around 83°C. It is formed from nickel bromide and tetra-n-butylammonium bromide in

ethyl alcohol.[7]

Tetraphenylphosphonium tetrabromonickelate(II) can be made from

nickel bromide, triphenylphosphine, and bromobenzene by heating them together in a sealed tube at 250 °C. This substance is dark blue. If it is heated over 260° the color changes to green, and it melts at 273 °C.[1][8]

A dark blue oil, bis-(o-tolyltriethylphosphonium) tetrabromonickelate (o-CH3C6H6PEt3)2NiBr4 can be made from the reaction of o-tolyl bis-triethylphosphine, nickel bromide and o-tolyl bromide. (o-CH3OC6H6PEt3)2NiBr4 and (C6H5PEt3)2NiBr4 are made in a similar way.[9]

bis-(benzo[e]-1,3-dithiepan-2-diethylimmonium) tetrabromonickelate, abbreviated as (xdtc)2NiBr4, has dark blue crystals that melt at 166 °C. It is made from α,α'-dibromo-o-xylene and bis-(N,N-diethyldithiocarbamato)nickel(II) dissolved in 1,2-dichloroethane.[10]

bis-(tetra-n-butylphosphonium) tetrabromonickelate can form as a glass when nickel bromide is dissolved in molten tetra-n-butylphosphonium iodide.[11]

Blue 1,1,1-trimethylhydrazinium tetrabromonickelate [H2NN(CH3)3]2NiBr4 is a salt stable between 70° and 260 °C. It can be formed by heating an octahedral neutral nickel complex where the trimethylhydrazinium and bromide are all ligands on a nickel atom. The salt decomposes at room temperature to polymeric trimethylhydrazinium nickel tribromide. The salt decomposes when dissolved in polar solvents, due to solvolysis.[12]

Related

One bromine atom can be substituted by other ligands, such as triphenylphosphine, to make a dark green triphenylphosphinetribromonickelate ion.[8] Analogous tetrahedral nickelates include

tetracyanonickelates
.

References

  1. ^
    doi:10.1021/ja01481a014
    .
  2. ^
    doi:10.1021/ic50025a019
    .
  3. ISBN 978-0471936237. {{cite book}}: |journal= ignored (help
    )
  4. doi:10.1021/ac60264a010
    .
  5. doi:10.1016/0020-1650(71)80078-8
    .
  6. doi:10.1039/JR9590003997
    .
  7. doi:10.1021/ja01076a014
    .
  8. ^
    doi:10.1021/ja01463a021
    .
  9. doi:10.1021/ja00519a015
    .
  10. doi:10.1021/ic50156a044
    .
  11. doi:10.1021/ja00844a018
    .
  12. doi:10.1021/ic50106a011
    .
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