Copper(II) tetrafluoroborate explained

Copper(II) tetrafluoroborate is any inorganic compound with the formula Cu(H₂O)_x(BF₄)₂. As usually encountered, it is assumed to be the hexahydrate (x = 6), but this salt can be partially dehydrated to the tetrahydrate. Regardless, these compounds are aquo complexes of copper in its +2 oxidation state, with two weakly coordinating tetrafluoroborate anions.

The compound is used in organic synthesis, e.g. as a Lewis acid for Diels Alder reactions, for cyclopropanation of alkenes with diazo reagents, and as a Lewis Acid in Meinwald Rearrangement reactions on Epoxides.^[1] In the former two applications, the copper(II) is reduced to a copper(I) catalyst.^{[2] [3]} The compound is also used for copper electroplating in fluoroborate-based plating baths.^[4]

Notes and References

1. Robinson. Mathew W.C.. Pillinger. Kathryn S.. Graham. Andrew E.. August 2006. Highly efficient Meinwald rearrangement reactions of epoxides catalyzed by copper tetrafluoroborate. Tetrahedron Letters. 47. 33. 5919–5921. 10.1016/j.tetlet.2006.06.055.
2. Ilhyong Ryu, Noboru Sonoda, "Copper(II) Tetrafluoroborate" Encyclopedia of Reagents for Organic Synthesis 2001, John Wiley & Sons.
3. http://chemicalland21.com/industrialchem/inorganic/COPPER%20%28II%29%20TETRAFLUOROBORATE.htm Copper(II) Tetrafluorborate
4. Barauskas . Romualdas "Ron" . Copper plating . Metal Finishing . January 1, 2000 . 98 . 1 . 234–247 . 10.1016/S0026-0576(00)80330-X . July 21, 2022 . en . 0026-0576.