Copper(II) tetrafluoroborate

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Copper(II) tetrafluoroborate[1]
Copper tetrafluoroborate.svg
IUPAC name
Copper(II) tetrafluoroborate
3D model (JSmol)
ECHA InfoCard 100.049.037
Molar mass 237.155 g/mol
Appearance blue crystal
soluble in water
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 1 mg/m3 (as Cu)[2]
REL (Recommended)
TWA 1 mg/m3 (as Cu)[2]
IDLH (Immediate danger)
TWA 100 mg/m3 (as Cu)[2]
Related compounds
Other anions
Copper(II) chloride
Copper(II) oxide
Copper(II) triflate
Other cations
Sodium tetrafluoroborate
Lithium tetrafluoroborate
Silver tetrafluoroborate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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.[3] 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.[4] In the former two applications, the copper(II) is reduced to a copper(I) catalyst.[3][5]


  1. ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, pp. 4–56, ISBN 0-8493-0594-2
  2. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0150". National Institute for Occupational Safety and Health (NIOSH).
  3. ^ a b Ilhyong Ryu, Noboru Sonoda, "Copper(II) Tetrafluoroborate" Encyclopedia of Reagents for Organic Synthesis 2001, John Wiley & Sons. doi:10.1002/047084289X.rc249
  4. ^ 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. doi:10.1016/j.tetlet.2006.06.055.
  5. ^ Copper(II) Tetrafluorborate,