Organotrifluoroborate

General structural formula of an organotrifluoroborate anion

Organotrifluoroborates are organoboron compounds that contain an anion with the general formula [RBF₃]⁻. They can be thought of as protected boronic acids, or as adducts of carbanions and boron trifluoride. Organotrifluoroborates are tolerant of air and moisture^[1] and are easy to handle and purify.^[2] They are often used in organic synthesis as alternatives to boronic acids (RB(OH)₂), boronate esters (RB(OR′)₂), and organoboranes (R₃B), particularly for Suzuki-Miyaura coupling.^[3][4]

Structure

thermal ellipsoid model of [PhBF3]−, as found in the crystal structure of K[PhBF3][5]	space-filling packing diagram of the crystal structure of K[PhBF3][5]

Synthesis

See also: Organoboron chemistry#Borates

Boronic acids RB(OH)₂ react with potassium bifluoride K[HF₂] to form trifluoroborate salts K[RBF₃].

Mechanism

The mechanism of organotrifluoroborate-based Suzuki-Miyaura coupling reactions has recently been investigated in detail. The organotrifluoroborate hydrolyses to the corresponding boronic acid in situ, so a boronic acid can be used in place of an organotrifluoroborate, as long as it is added slowly and carefully.^[6][7]

References

1. ^ "Alfa Aesar – Product Flyers & Technical Reviews – Organotrifluoroborates". http://www.alfa.com/en/docs/Organotrifluoroborates.pdf. 
2. ^ "Sigma-Aldrich – Chemical Synthesis – Technology Spotlights – Organotrifluoroborates". http://www.sigmaaldrich.com/chemistry/chemical-synthesis/technology-spotlights/organotrifluoroborates.html. 
3. ^ Darses, Sylvain; Genet, Jean-Pierre (2008). "Potassium Organotrifluoroborates: New Perspectives in Organic Synthesis". Chem. Rev. 108 (1): 288–325. doi:10.1021/cr0509758. PMID 18095714. 
4. ^ Molander, Gary A.; Ellis, Noel (2007). "Organotrifluoroborates: Protected Boronic Acids That Expand the Versatility of the Suzuki Coupling Reaction". Acc. Chem. Res. 40 (4): 275–286. doi:10.1021/ar050199q. PMID 17256882. 
5. ^ ^{a b} Conole, G.; Clough, A.; Whiting, A. (1995). "Potassium Trifluorophenylborate". Acta Cryst. C 51: 1056–1059. doi:10.1107/S0108270194014198. 
6. ^ Butters, M.; Harvey, J. N.; Jover, J.; Lennox, A. J. J.; Lloyd-Jones, G. C.; Murray, P. M. (2010). "Aryl Trifluoroborates in Suzuki-Miyaura Coupling: The Roles of Endogenous Aryl Boronic Acid and Fluoride". Angew. Chem. Int. Ed. 49 (30): 5156–60. doi:10.1002/anie.201001522. PMID 20544767. 
7. ^ "Mechanism Of Suzuki-Miyaura Coupling Revealed". Chemical & Engineering News. http://pubs.acs.org/isubscribe/journals/cen/88/i26/html/8826scic6.html. Retrieved 2010-06-27. 

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