Formula [Cu(CH3CN)4]PF6 Appearance White powder | Molar mass 372.7198 g/mol | |
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Tetrakis(acetonitrile)copper(I) hexafluorophosphate is a coordination compound with the formula [Cu(CH3CN)4]PF6. It is a colourless solid that is used in the synthesis of copper complexes.
Contents
Structure
As confirmed by X-ray crystallographic studies, copper(I) ion is coordinated to four almost linear acetonitrile ligands in a nearly ideal tetrahedral geometry. Related complexes are known with other anions including the perchlorate, tetrafluoroborate, and nitrate. With the weakly coordinating anion B(C6F5)4−, salts of [Cu(CH3CN)2]+ are obtained.
The acetonitrile ligands protect the Cu+ ion from oxidation to Cu2+. However, acetonitrile is not bound very strongly to the copper ion, thus the complex is a useful source of Cu(I).
Synthesis
The cation was first reported in 1923 with a nitrate anion as a byproduct of the reduction of silver nitrate with a suspension of copper powder in acetonitrile. [Cu(CH3CN)4]PF6 is generally produced by the addition of HPF6 to a suspension of copper(I) oxide in acetonitrile:
Cu2O + 2 HPF6 + 8 CH3CN → 2 [Cu(CH3CN)4]PF6 + H2OThe 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 a Cu2+ species.
Reactions and applications
As the coordinated acetonitrile ligands may be displaced in other solvents, the [Cu(CH3CN)4]PF6 compound may serve as a precursor in the non-aqueous syntheses of other Cu(I) compounds.
Water-immiscible organic nitriles have been shown to selectively extract Cu2+ 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 [Cu(CH3CN)4]+ + 6 H2O → [Cu(H2O)6]2+ + Cu + 8 CH3CN