Sodium tetraphenylborate

Chembox new
ImageFile = NaBPh4.png IUPACName = Sodium tetraphenylborate
OtherNames = Tetraphenylboron sodium
Section1 = Chembox Identifiers
CASNo = 143-66-8
Section2 = Chembox Properties
Formula = (C₆H₅)_{4BNa
MolarMass = 324.24 g/mol
Appearance = white solid
Solubility = 47 g/100 g water
MeltingPt = >300 °C}
Section7 = Chembox Hazards
MSDS = []
SPhrases =

Sodium tetraphenylborate is the chemical compound with the formula NaB(C₆H₅)₄. It is a salt, wherein the anion consists of four phenyl rings bonded to boron. This crystalline solid is used to prepare other tetraphenylborate salts, which are often highly soluble soluble in organic solvents. The compound is frequently used in inorganic and organometallic chemistry as a precipitating agent.

ynthesis

Sodium tetraphenylborate is synthesized by the reaction between sodium tetrafluroborate and phenylmagnesium bromide. [cite journal | journal = Organometallics | year = 2005 | pages = 3579 | doi = 10.1021/om0501428 | title = Safe Preparation and Purification of Sodium Tetrakis [(3,5-trifluoromethyl)phenyl] borate (NaBArF₂₄): Reliable and Sensitive Analysis of Water in Solutions of Fluorinated Tetraarylborates. | author = N. Yakelis and R. G. Bergman] :NaBF₄ + 4 PhMgBr → 2 MgBr₂ + 2 MgF₂2 + NaBPh₄Unlike smaller counteranions, such as nitrate and the halides, tetraphenylborate confers lipophilicity to its salts. Many analogues tetraarylborates have been synthesized, containing both electron rich and electron deficient aryl groups.

Use in chemical synthesis

Prepartion of N-acylammonium salts

Addition of sodium tetraphenylborate to a solution of a tertiary amine and an acid chloride in acetonitrile gives the acylonium salt by precipitating NaCl from the reaction mixture. This method has a broad scope: [cite journal | journal = J. Org. Chem. | year = 1992 | pages = 5136 | doi =10.1021/jo00045a025 | title = Preparation and characterization of crystalline N-acylammonium salts. | author = J. King and G. Bryant]

Sodium tetraphenylborate is also employed as a phenyl donor in palladium-catalyzed cross-coupling reactions involving vinyl and aryl triflates to give arylalkenes and biaryl compoundsin good yields and under mild conditions, respectively. [cite journal | journal = Tetrahedron Letters | year = 1992 | pages = 4815 | doi = 10.1016/S0040-4039(00)61293-5 | title = Palladium-catalyzed cross-coupling reactions of vinyl and aryl triflates with tetraarylborates. | author = P. Ciattini, E. Morera, G. Ortar] :RC(O)Cl + R'₃N + NaB(C₆H₅)₄ → [RC(O)NR'₃] [B(C₆H₅)₄] + NaCl

Coordination chemistry

Tetraphenylborates are often studied in organometallic chemistry because of their favorable solubility in nonpolar solvents and their crystallinity. For example, pentakis(trimethylphosphite) complexes of d⁸ metals (Ni, Pd, and Pt) have been prepared as their tetraphenylborate salts. [cite journal | journal = Inorganic Syntheses| year = 2007 | pages = 76 | doi = 10.1002/9780470132517.ch22 | title = Pentakis(Trimethyl Phosphite) Complexes of the d⁸ Transition Metals | author = J. Jesson, M. Cushing, S. D. Ittel] Similarly, sodium tetraphenylborate has been used to isolate metal complexes containing dinitrogen. [cite journal | journal = Inorg. Synth. | volume = 15 | year = 1974 | pages = 21 | doi = 10.1002/9780470132463.ch6 | title = trans - (Dinitrogen) Bis [Ethylenebis(diethylphosphine)] Hydridoiron(II) Tetraphenylborate. | author =M. Mays and E. Prater] In the reaction below, sodium tetraphenylborate allows N₂ to displace the chloride ligand, which is removed from solution as a precipitate of sodium chloride.:FeHCl(diphosphine)₂ + NaB(C₆H₅)₄ + N₂ → [FeH(N₂)(diphosphine)₂] [B(C₆H₅)₄] + NaCl

References