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| Names | |
|---|---|
| IUPAC name Sodium tetraphenylborate | |
| Other names Tetraphenylboron sodium | |
| Identifiers | |
| CAS Number | |
| ECHA InfoCard | 100.005.096 
|
| PubChem CID | |
| CompTox Dashboard (EPA) | |
| Properties | |
| Chemical formula | (C6H5)4BNa |
| Molar mass | 342.22 g/mol |
| Appearance | white solid |
| Melting point | >300 °C |
| Solubility in water | 47 g/100 g water |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa).
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Infobox references
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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.
Synthesis
Sodium tetraphenylborate is synthesized by the reaction between sodium tetrafluoroborate and aryl Grignard reagents:
- NaBF4 + 4 ArMgBr → 2 MgBr2 + 2 MgF2 + NaBAr4 (where Ar = aryl)
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.
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 → + 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 {M5} (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 → B(C6H5)4 + NaCl
The use of tetraphenylborate is limited to non-acidic cations, strong acids decompose this anion to triphenylborane and benzene:
- H + B(C6H5)4 → B(C6H5)3 + C6H6
References
- W. E. Buschman, J. S. Miller (2002). "Synthesis of (M = V, Cr, Mn, Fe, Co, Ni) Salts of Tetraborate". Inorganic Syntheses. 33: 83. doi:10.1002/0471224502.ch2. ISBN 0471208256.
{{cite journal}}:|chapter=ignored (help) - J. King and G. Bryant (1992). "Preparation and characterization of crystalline N-acylammonium salts". J. Org. Chem. 57 (19): 5136. doi:10.1021/jo00045a025.
- P. Ciattini, E. Morera, G. Ortar (1992). "Palladium-catalyzed cross-coupling reactions of vinyl and aryl triflates with tetraarylborates". Tetrahedron Letters. 33 (33): 4815. doi:10.1016/S0040-4039(00)61293-5.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - J. P. Jesson, M. Cushing, S. D. Ittel (2007). "Pentakis(Trimethyl Phosphite) Complexes of the d Transition Metals". Inorganic Syntheses. Inorganic Syntheses. 20: 76. doi:10.1002/9780470132517.ch22. ISBN 9780470132517.
{{cite journal}}:|chapter=ignored (help)CS1 maint: multiple names: authors list (link) - M. Mays and E. Prater (1974). "trans - (Dinitrogen) Bis Hydridoiron(II) Tetraphenylborate". Inorg. Synth. Inorganic Syntheses. 15: 21. doi:10.1002/9780470132463.ch6. ISBN 9780470132463.
{{cite journal}}:|chapter=ignored (help) - Tianshu Li, Alan J. Lough, Cristiano Zuccaccia, Alceo Macchioni, and Robert H. Morris "An acidity scale of phosphonium tetraphenylborate salts and ruthenium dihydrogen complexes in dichloromethane" Can. J. Chem. 84(2): 164–175 (2006). doi:10.1139/V05-236.