Sodium tetraphenylborate
Encyclopedia
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 colourless 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
.
and aryl Grignard reagents
:
Unlike 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.
gives the acylonium salt by precipitating NaCl from the reaction mixture. This method has a broad scope:
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.
. In the reaction below, sodium tetraphenylborate allows N2 to displace the chloride ligand, which is removed from solution as a precipitate of sodium chloride:
The use of tetraphenylborate is limited to non-acidic cations, strong acids decompose this anion to triphenylborane
and benzene
:
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the formula NaB(C6H5)4. It is a salt, wherein the anion consists of four phenyl rings bonded to boron. This colourless 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
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
.
Synthesis
Sodium tetraphenylborate is synthesized by the reaction between sodium tetrafluoroborateSodium tetrafluoroborate
Sodium tetrafluoroborate, also called sodium borofluoride, is a compound with formula NaBF4. It forms colorless water-soluble rhombic crystals and is soluble in water and less soluble in organic solvents....
and aryl Grignard reagents
Phenylmagnesium bromide
Phenylmagnesium bromide, with the simplified formula , is a magnesium-containing organometallic compound. It is so commonly used that it is commercially available as a solution in diethyl ether or tetrahydrofuran . Phenylmagnesium bromide is a Grignard reagent...
:
- NaBF4 + 4 ArMgBr → 2 MgBr2 + 2 MgF2 + NaBAr4 (where Ar = arylAreneArene or Arênê or Arène may refer to:*an aromatic hydrocarbon*Arene , a genus of marine snails in the family Areneidae*Arene , the wife of Aphareus and mother of Idas and Lynceus in Greek mythology...
)
Unlike 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.
Preparation of N-acylammonium salts
Addition of sodium tetraphenylborate to a solution of a tertiary amine and an acid chloride in acetonitrileAcetonitrile
Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...
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 ligandsDinitrogen complex
Metal dinitrogen complexes are a coordination compounds that contain the dinitrogen as a ligand. In the area of coordination chemistry, the atomic and diatomic forms of nitrogen are distinguished, although otherwise "nitrogen" refers to N2....
. 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, strong acids decompose this anion to triphenylborane
Triphenylborane
Triphenylborane, often abbreviated to BPh3 where Ph is the phenyl group C6H5-, is a chemical compound with the formula B3. It is a white crystalline solid and is both air and moisture sensitive, slowly forming benzene and triphenylboroxine. It is soluble in aromatic solvents.-Structure and...
and benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
:
- H+ + B(C6H5)4- → B(C6H5)3 + C6H6