Tetrakis(acetonitrile)copper(I) hexafluorophosphate is a salt with the formula u(CH₃CN)₄F₆. It is a colourless solid that is used in the synthesis of other copper complexes. The cation u(CH₃CN)₄sup>+ is a well-known example of a

transition metal nitrile complex Transition metal nitrile complexes are coordination compounds containing nitrile ligands. Because nitriles are weakly basic, the nitrile ligands in these complexes are often labile. Scope of nitriles Typical nitrile ligands are acetonitrile, prop ...

.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.

Structure

As confirmed by X-ray crystallographic studies, the copper(I) ion is coordinated to four almost linear acetonitrile ligands in a nearly ideal tetrahedral geometry. Similar complexes with other anions including the perchlorate,

tetrafluoroborate Tetrafluoroborate is the anion . This tetrahedral species is isoelectronic with tetrafluoroberyllate (), tetrafluoromethane (CF4), and tetrafluoroammonium () and is valence isoelectronic with many stable and important species including the perchl ...

, and

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

are known.

Synthesis

The cation was first reported in 1923 with a nitrate anion as a byproduct of the reduction of

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar caustic' ...

with a suspension of copper powder in acetonitrile. u(CH₃CN)₄F₆ is generally produced by the addition of HPF₆ to a suspension of

copper(I) oxide Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper, the other being or copper(II) oxide or cupric oxide (CuO). This red-coloured solid is a component of some antifoulin ...

in acetonitrile: :Cu₂O + 2 HPF₆ + 8 CH₃CN → 2 u(CH₃CN)₄F₆ + H₂O 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 Cu²⁺ impurities.

Reactions and applications

The acetonitrile ligands protect the Cu⁺ ion from oxidation to Cu²⁺, but are rather poorly bound: with other counterions, the complex forms di- and tri-acetonitrilo complexes and is also a useful source of unbound Cu(I). Water-immiscible organic nitriles have been shown to selectively extract Cu(I) from aqueous chloride solutions. Through this method, copper can be separated from a mixture of other metals. Dilution of acetonitrile solutions with water induces disproportionation: :2 u(CH₃CN)₄sup>+ + 6 H₂O → u(H₂O)₆sup>2+ + Cu + 8 CH₃CN

References

{{Hexafluorophosphates Copper complexes Hexafluorophosphates