CAS NO:143-66-8  Sodium tetraphenylborate

IUPAC name:Sodium tetraphenylborate

Other names:Tetraphenylboron sodium

CAS Registry Number:143-66-8 

Chemical formula:(C6H5)4BNa

Molar mass:342.216 g/mol

Appearance:white solid

Melting point > 300 °C (572 °F; 573 K)

Solubility in water:47 g/100 mL

Solubility:soluble in ethanol

Introduction:

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

Use in chemical synthesis

Preparation 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:

RC(O)Cl + R'3N + NaB(C6H5)4 → [RC(O)NR'3][B(C6H5)4] + NaCl

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 compounds in good yields and under mild conditions, respectively.

Use in coordination chemistry

Tetraphenylborates are often studied in organometallic chemistry because of their favorable solubility in nonpolar solvents and their crystallinity. For example, the homoleptic trimethylphosphite complexes {M[P(OCH3)3]5}2+ (Ni, Pd, and Pt) have been prepared as their tetraphenylborate salts.Similarly, sodium tetraphenylborate has been used to isolate complexes containing dinitrogen ligands. 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

The use of tetraphenylborate is limited to non-acidic cations. With strong acids, the anion undergoes protonolysis to give triphenylborane and benzene:[8]

H+ + B(C6H5)4- → B(C6H5)3 + C6H6