tetrachloronickelate

File:Tetrachloronickelate(II)-3D-balls.png

Tetrachloronickelate is the metal complex with the formula [NiCl₄]²⁻. Salts of the complex are available with a variety of cations, but a common one is tetraethylammonium.{{cite book|author=Naida S. Gill |author2=F. B. Taylor |chapter=Tetrahalo Complexes of Dipositive Metals in the First Transition Series |year=1967 |volume=9 |pages=136–142 |doi=10.1002/9780470132401.ch37 |title=Inorganic Syntheses |isbn=978-0-470-13240-1}}

File:(Et4N)2NiCl4.jpg

When concentrated lithium chloride and nickel chloride solution in water is mixed, only a pentaaquachloro complex is formed: [Ni(H₂O)₅Cl]⁺. However in other organic solvents, or molten salts the tetrachloronickelate ion can form. Nickel can be separated from such a solution in water or methanol, by partitioning it into a cyclohexane solution of amines.{{cite journal|last1=Florence|first1=T. M.|last2=Farrar|first2=Yvonne J.|title=Liquid-liquid extraction of nickel with long-chain amines from aqueous and nonaqueous halide media|journal=Analytical Chemistry|date=July 1968|volume=40|issue=8|pages=1200–1206|doi=10.1021/ac60264a010}}

Organic ammonium salts of the type (R₃NH)₂[NiCl₄] are often thermochromic (R = Me, Et, Pr). Near room temperature, these salts are yellow , but these solids become blue when heated to near 70 °C. The bright blue color is characteristic of tetrahedral [NiCl₄]²⁻, the intensity being a consequence of the Laporte selection rule. The yellow color results from a polymer consisting of octahedral Ni centers. The corresponding tetrabromonickelates are also thermochromic with a lower transition temperatures.{{cite journal|last1=Ferraro|first1=John R.|last2=Sheren|first2=Anne T.|title=Some new thermochromic complexes of Nickel(II) of the type [R/sub x/NH/sub 4-x/]2NiCl4|journal=Inorganic Chemistry|volume=17|issue=9|pages=2498–2502|date=3 February 1978|doi=10.1021/ic50187a032}}

History

The blue colour due to the tetrachloronickelate ion was first observed in 1944 when Remy and Meyer melted caesium chloride and caesium nickel trichloride together.

Compounds

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!formula

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!Remarks

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Cs₂NiCl₄

|caesium tetrachloronickelate

|blue, stable only over 70°

[(CH₃)₄N]₂NiCl₄

|Tetramethylammonium tetrachloronickelate

|dark blue

|{{cite journal|last1=Cotton|first1=F. A.|last2=Faut|first2=O. D.|last3=Goodgame|first3=D. M. L.|title=Preparation, Spectra and Electronic Structures of Tetrahedral Nickel(II) Complexes Containing Triphenylphosphine and Halide Ions as Ligands|journal=Journal of the American Chemical Society|date=January 1961|volume=83|issue=2|pages=344–351|doi=10.1021/ja01463a021|bibcode=1961JAChS..83..344C }}

[(C₂H₅)₄N]₂NiCl₄

|Tetraethylammonium tetrachloronickelate

|{{cite journal|last1=Inman|first1=Guy W.|last2=Hatfield|first2=William E.|last3=Jones|first3=Edwin R.|title=The magnetic properties of tetraethylammonium tetrachloronickelate(II) and tetraethylammonium tetrabromonickelate(II)|journal=Inorganic and Nuclear Chemistry Letters|date=August 1971|volume=7|issue=8|pages=721–723|doi=10.1016/0020-1650(71)80078-8}}{{cite journal|last1=Gill|first1=Naida S.|last2=Nyholm|first2=R. S.|title=802. Complex halides of the transition metals. Part I. Tetrahedral nickel complexes|journal=Journal of the Chemical Society (Resumed)|date=1959|pages=3997|doi=10.1039/JR9590003997}}

[H₂NN(CH₃)₃]₂NiCl₄

|1,1,1-trimethylhydrazinium tetrachloronickelate

|blue, only stable over 145 °C, under this is yellow

|{{cite journal|last1=Goedken|first1=V. L.|last2=Vallarino|first2=L. M.|last3=Quagliano|first3=J. V.|title=Cationic ligands. Coordination of the 1,1,1-trimethylhydrazinium cation to nickel(II)|journal=Inorganic Chemistry|date=December 1971|volume=10|issue=12|pages=2682–2685|doi=10.1021/ic50106a011}}

[(C₆H₅)₄As]₂NiCl₄

|bis-tetraphenylarsonium tetrachloronickelate

|blue, melts at 199.5°C

[(C₆H₅)₃CH₃As]₂NiCl₄

|bis-triphenylmethylarsonium tetrachloronickelate

|blue

[C₂mim]₂NiCl₄

|1-ethyl-3-methylimidazolium tetrachloronickelate(II)

|tetragonal I4₁/a a=14.112 c=19.436 V=3871.1 Z=8 density=1.47 MW=422.84

|melts at 92°

|{{cite journal|last1=Hitchcock|first1=Peter B.|last2=Seddon|first2=Kenneth R.|last3=Welton|first3=Thomas|title=Hydrogen-bond acceptor abilities of tetrachlorometalate(II) complexes in ionic liquids|journal=Journal of the Chemical Society, Dalton Transactions|date=1993|issue=17|pages=2639|doi=10.1039/DT9930002639}}

[C₄mim]₂NiCl₄

|1-butyl-3-methylimidazolium tetrachloronickelate(II)

|dark blue, melts at 56°C

|{{cite journal|last1=Meredith|first1=M. Brett|last2=McMillen|first2=C. Heather|last3=Goodman|first3=Jonathan T.|last4=Hanusa|first4=Timothy P.|title=Ambient temperature imidazolium-based ionic liquids with tetrachloronickelate(II) anions|journal=Polyhedron|date=August 2009|volume=28|issue=12|pages=2355–2358|doi=10.1016/j.poly.2009.04.037}}

[C₅mim]₂NiCl₄

|1-pentyl-3-methylimidazolium tetrachloronickelate(II)

|dark blue liquid

[C₆mim]₂NiCl₄

|1-hexyl-3-methylimidazolium tetrachloronickelate(II)

|dark blue liquid

[C₇mim]₂NiCl₄

|1-heptyl-3-methylimidazolium tetrachloronickelate(II)

|dark blue liquid

[C₈mim]₂NiCl₄

|1-octyl-3-methylimidazolium tetrachloronickelate(II)

|dark blue liquid

[NH₃CH₂CH₂NH₃]NiCl₄

|ethylenediammonium tetrachloronickelate(II)

|perovskite layered, space group P2₁/c a=8.441, b=6.995, c=6.943, β=92.925 Z=2

|brown, isostructural with Mn, Cu, Pd, and Cd compounds

|{{cite journal|last1=Skaarup|first1=Steen|last2=Berg|first2=Rolf Willestofte|title=Structural properties and vibrational spectra of the ethylene-diammonium family of perovskite layer-type crystals: [NH3CH2CH2NH3] [MCl4], M = Ni, Pd, Cu, Cd, Mn|journal=Journal of Solid State Chemistry|date=September 1978|volume=26|issue=1|pages=59–67|doi=10.1016/0022-4596(78)90133-0|bibcode=1978JSSCh..26...59S }}

Related substances

tetrabromonickelates

References

Category:Nickel complexes

Category:Inorganic chlorine compounds

Category:Chlorometallates