View source for Chemistry:Tetrakis(acetonitrile)copper(I) hexafluorophosphate

{{Chembox
| Watchedfields = changed
| verifiedrevid = 396377376
| ImageFile = Tetrakis(acetonitrile)copper(I) hexafluorophosphate.png
| ImageSize = 260
| ImageAlt = Structural formulas of the tetrakis(acetonitrile)copper(I) cation and the hexafluorophosphate anion
| ImageFile1 = Tetrakis(acetonitrile)copper(I) hexafluorophosphate 3D spacefill.png
| ImageSize1 = 220
| ImageAlt1 = Space-filling models of the component ions of tetrakis(acetonitrile)copper(I) hexafluorophosphate
| IUPACName = Tetrakis(acetonitrile)copper(I) hexafluorophosphate
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 64443-05-6
| PubChem = 11068737
}}
|Section2={{Chembox Properties
| Formula = [Cu(CH<sub>3</sub>CN)<sub>4</sub>]PF<sub>6</sub>
| MolarMass = 372.7198 g/mol
| Appearance = White powder
| MeltingPtC = 160
}}
}}

'''Tetrakis(acetonitrile)copper(I) hexafluorophosphate''' is a salt with the formula [Cu(CH<sub>3</sub>CN)<sub>4</sub>]PF<sub>6</sub>. It is a colourless solid that is used in the synthesis of other copper complexes. The cation [Cu(CH<sub>3</sub>CN)<sub>4</sub>]<sup>+</sup> is a well-known example of a transition metal nitrile complex.<ref name=Rach>Silvana F. Rach, Fritz E. Kühn "Nitrile Ligated Transition Metal Complexes with Weakly Coordinating Counteranions and Their Catalytic Applications" Chem. Rev., 2009, volume 109, pp 2061–2080. {{doi|10.1021/cr800270h}}</ref>

==Structure==
As confirmed by [[Physics:X-ray crystallography|X-ray crystallographic studies]], the copper(I) ion is coordinated to four almost linear acetonitrile ligands in a nearly ideal tetrahedral geometry.<ref>{{cite journal | author = Kierkegaard C.P. |author2=Norrestam R.  | year = 1975 |title = Copper(I) tetraacetonitrile perchlorate | journal = Acta Crystallogr. B | volume = 31| pages = 314–317 | doi = 10.1107/S0567740875002634}}</ref><ref>{{cite journal|doi=10.1107/S0108270194012527|title=Tetrakis(acetonitrile-N)copper(I) Hexafluorophosphate(V) Acetonitrile Solvate|year=1995|last1=Black|first1=J. R.|last2=Levason|first2=W.|last3=Webster|first3=M.|journal=Acta Crystallographica Section C Crystal Structure Communications|volume=51|issue=4|pages=623–625}}</ref>  Similar complexes with other anions including the perchlorate, [[Chemistry:Tetrafluoroborate|tetrafluoroborate]], and [[Chemistry:Nitrate|nitrate]] are known.<ref name=Rach/>  

==Synthesis==
The cation was first reported in 1923 with a nitrate anion as a byproduct of the reduction of [[Chemistry:Silver nitrate|silver nitrate]] with a suspension of copper powder in acetonitrile.<ref>{{cite journal| author = Morgan, H.H. | year = 1923 | title = Preparation and Stability of Cuprous Nitrate and Other Cuprous Salts in the Presence of Nitriles | journal = J. Chem. Soc. | volume = 19| pages = 2901 | doi = 10.1039/CT9232302901 | last2 = Sand | first2 = Henry Julics Salomon}}</ref> [Cu(CH<sub>3</sub>CN)<sub>4</sub>]PF<sub>6</sub> is generally produced by the addition of HPF<sub>6</sub> to a suspension of [[Chemistry:Copper(I) oxide|copper(I) oxide]] in acetonitrile:<ref name="Kubas1979"/>
:Cu<sub>2</sub>O + 2 HPF<sub>6</sub> + 8 CH<sub>3</sub>CN → 2 [Cu(CH<sub>3</sub>CN)<sub>4</sub>]PF<sub>6</sub> + H<sub>2</sub>O
The reaction is highly exothermic, and may bring the solution to a boil. Upon crystallization, the resulting microcrystals should be white, though a blue tinge is common, indicating the presence of Cu<sup>2+</sup> impurities.<ref name="Kubas1979">{{cite journal | author = Kubas, G.J. | year = 1990 | title = Tetrakis(acetonitirile)copper(I) Hexaflurorophosphate | journal = [[Chemistry:Inorganic Syntheses|Inorganic Syntheses]] | volume = 28 | pages = 68–69 | doi = 10.1002/9780470132593.ch15}}</ref>

==Reactions and applications==
The acetonitrile ligands protect the Cu<sup>+</sup> ion from oxidation to Cu<sup>2+</sup>, but are rather poorly bound: with other counterions, the complex forms di-<ref name=Rach/> and tri-acetonitrilo<ref>{{cite journal |doi=10.1039/C8DT03723J|title=Highly soluble Cu(i)-acetonitrile salts as building blocks for novel phosphorus-rich organometallic-inorganic compounds|year=2018|last1=Elsayed Moussa|first1=Mehdi|last2=Piesch|first2=Martin|last3=Fleischmann|first3=Martin|last4=Schreiner|first4=Andrea|last5=Seidl|first5=Michael|last6=Scheer|first6=Manfred|journal=Dalton Transactions|volume=47|issue=45|pages=16031–16035|pmid=30321246|url=https://epub.uni-regensburg.de/38440/1/Scheer%2C%20RSC%2C%20Dalton%20Transactions.pdf}}</ref> complexes and is also a useful source of unbound Cu(I).<ref name="Kubas1979" />  

Water-immiscible organic nitriles have been shown to selectively extract Cu(I) from aqueous chloride solutions.<ref>{{cite journal | author = Preston, J. S. |author2=Muhr D. M|author3=Parker A. J. | year = 1980 | title = Cuprous hydrometallurgy: Part VIII. Solvent extraction and recovery of copper(I) chloride with organic nitriles from an iron(III), copper(II) chloride, two-step oxidative leach of chalcopyrite concentrate | journal = [[Chemistry:Hydrometallurgy|Hydrometallurgy]] | volume = 5| pages = 227| doi = 10.1016/0304-386X(80)90041-9}}</ref> Through this method, copper can be separated from a mixture of other metals.  Dilution of acetonitrile solutions with water induces disproportionation:
:2 [Cu(CH<sub>3</sub>CN)<sub>4</sub>]<sup>+</sup> + 6 H<sub>2</sub>O → [Cu(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> + Cu + 8 CH<sub>3</sub>CN

==References==
{{reflist}}

{{Hexafluorophosphates}}

[[Category:Copper complexes]]
[[Category:Hexafluorophosphates]]

{{Sourceattribution|Tetrakis(acetonitrile)copper(I) hexafluorophosphate}}