Trimethylborane
 | |
| Names | |
|---|---|
| IUPAC name
Trimethylborane | |
| Other names
trimethylborine, trimethylboron | |
| Identifiers | |
593-90-8  | |
| ChemSpider | 62201  |
| EC number | 209-816-3 |
| |
| Jmol-3D images | Image |
| |
| Properties | |
| C3H9B | |
| Molar mass | 55.92 g/mol |
| Appearance | Colorless gas or liquid |
| Density | 0.625 g/cm3 at -100 °C[1] |
| Melting point | −161.5 °C (−258.7 °F; 111.6 K) |
| Boiling point | −20.2 °C (−4.4 °F; 253.0 K) |
| slight, Highly reactive | |
| Structure | |
| Molecular shape | Δ |
| Hazards | |
| Main hazards | Spontaneously flammable in air; causes burns |
| R-phrases | R17 R34[2] |
| S-phrases | S7 S23 S26 S36/37/39 S43 S45[2] |
| −40 °C (−40 °F; 233 K)[2] | |
| Related compounds | |
| Related compounds |
triethylborane Diborane methylborane |
| Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |
| verify (what is: /?) | |
| Infobox references | |
Trimethylborane (TMB) is a toxic, pyrophoric gas with the formula B(CH3)3 (which can also be written as Me3B, with Me representing methyl). Its melting point is -161.5 °C and its boiling point is -20.2 °C. Vapour pressure is given by log P = 6.1385+1.75 log T - 1393.3/T - 0.007735 T. T is temperature in Kelvin.[3] CAS number is 593-90-8.[4] Molecular weight is 55.914. The heat of vapourisation is 25.6 kJ/mol.[2]
Properties
As a liquid it is colourless. The strongest line in the infrared spectrum is at 1330 cm−1 followed by lines at 3010 cm−1 and 1185 cm−1.
Preparation
Trimethylborane was first made by Stock and Zeidler. Their method of preparation combined boron trichloride gas with dimethylzinc.[3] Although the substance can be prepared using Grignard reagents the output is contaminated by unwanted products from the solvent. Trimethylborane can be made on a small scale with a 98% yield by reacting trimethylaluminium in hexane with boron tribromide in dibutyl ether as a solvent.[3] Yet other methods are reacting tributyl borate with trimethylaluminium chloride, or potassium tetrafluoroborate with trimethylaluminium.[5] Yet another method is to add boron trifluoride in ether to methyl magnesium iodide.[6]
Reactions
Trimethylborane spontaneously ignites in air if the concentration is high enough. It burns with a green flame producing soot.[7]
Trimethylborane is a strong Lewis acid. It reacts with water and chlorine at room temperature. It also reacts with grease but not with Teflon or glass.[3] Trimethylborane can form an adduct with ammonia: (NH3):B(CH3)3.[8]
Trimethylborane reacts with diborane to disproportionate to form monomethyldiborane and dimethyldiborane: (CH3)BH2.BH3 and (CH3)2BH.BH3.
It reacts as a gas with trimethylphosphine to form a solid Lewis salt with a heat of formation of -41 kcal per mol. This adduct has a heat of sublimation of -24.6 kcal/mol. No reaction occurs with trimethylarsine or trimethylstibine.[6]
Methyl lithium reacting with the Trimethylborane produces a tetramethylborate salt: LiB(CH3)4.[9] The tetramethylborate ion has a negative charge and is isoelectronic with neopentane, tetramethylsilane, and the tetramethylammonium cation.
Use
Trimethylborane has been used as a neutron counter. For this use it has to be very pure.[8] It is also used in chemical vapour deposition where boron and carbon need to be deposited together.
References
- ↑ http://www.voltaix.com/images/doc/Msb000_TMB.pdf MSDS from Voltaix
- ↑ 2.0 2.1 2.2 2.3 Trimethylborane
- ↑ 3.0 3.1 3.2 3.3 William S. Rees, Jr. and al (1990). Alvin P. Ginsberg, ed. Trimethylborane. Inorganic Syntheses 27. p. 339.
- ↑ Graner, G., Hirota, E., Iijima, T., Kuchitsu, K., Ramsay, D. A., Vogt, J., Vogt, N.; Hirota; Iijima; Kuchitsu; Ramsay; Vogt; Vogt (2001). "C3H9B Trimethylborane". SpringerMaterials. Landolt-Börnstein - Group II Molecules and Radicals 25C: 1. doi:10.1007/10688787_381. ISBN 3-540-66774-1.
- ↑ Roland Koumlstera, Paul Bingera Wilhelm, V. Dahlhof; Binger; Dahlhoff (1973). "A Convenient Preparation of Trimethylborane and Triethylborane". Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry 3 (4): 359–367. doi:10.1080/00945717308057281.
- ↑ 6.0 6.1 Donald Charles Mente (May 1975). "The Reactions of Trimethyl group Va Lewis Bases with simple Boron Lewis Acids" (PDF).
- ↑ Herbert Ellern (1968). "Military and Civilian Pyrotechnics". Chemical Publishing Company. p. 24. CiteSeerX: 10
.1 ..1 .137 .1104 - ↑ 8.0 8.1 Gaylon S. Ross et al. (2 October 1961). "Preparation of High Purity Trimethylborane" (PDF). Journal of Research of the National Bureau of Standards Physics and Chemistry 66 (1).
- ↑ Georg Wittig in 1958