Tetrakis(acetonitrile)copper(I) hexafluorophosphate is a salt with the formula
3CN)4">u(CH3CN)4F
6. It is a colourless solid that is used in the synthesis of other copper complexes. The cation
3CN)4">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. 3CN)4">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 3CN)4">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 3CN)4">u(CH3CN)4sup>+ + 6 H2O → 2O)6">u(H2O)6sup>2+ + Cu + 8 CH3CN
References
{{Hexafluorophosphates
Copper complexes
Hexafluorophosphates