*** Welcome to piglix ***

Trimethylaluminium

Trimethylaluminium
Trimethylaluminium-3D-balls.png
Names
IUPAC name
Trimethylalane
Other names
Trimethylaluminium; aluminium trimethyl; aluminium trimethyl
Identifiers
3D model (Jmol)
ChemSpider
ECHA InfoCard 100.000.776
PubChem CID
Properties
C6H18Al2
Molar mass 144.17 g/mol
72.09 g/mol (C3H9Al)
Appearance Colorless liquid
Density 0.752 g/cm3
Melting point 15 °C (59 °F; 288 K)
Boiling point 125–130 °C (257–266 °F; 398–403 K)
reacts
Vapor pressure 1.2 kPa (20 °C)
9.24 kPa (60 °C)
Viscosity 1.12 cP (20 °C)
0.9 cP (30 °C)
Thermochemistry
155.6 J/mol·K
209.4 J/mol·K
−136.4 kJ/mol
-9.9 kJ/mol
Hazards
Main hazards Pyrophoric
GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H250, H260, H314
P222, P223, P231+232, P280, P370+378, P422
Highly Flammable FCorrosive C
R-phrases R14, R17, R34
S-phrases S16, S43, S45
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g., fluorine Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
Flash point −17.0 °C (1.4 °F; 256.1 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

Trimethylaluminium is one of the simplest examples of an organoaluminium compound. Despite its name it has the formula Al2(CH3)6 (abbreviated as Al2Me6 or TMA) as it exists as a dimer. This colorless liquid is an industrially important compound but must be handled with care due to its pyrophoricity; it evolves white smoke (aluminium oxides) when the vapor is released into the air.

Al2Me6 exists mostly as a dimer at room temperature and pressure, analogous in structure and bonding to diborane. As with diborane, the molecules are connected by 2 3-center-2-electron bonds: the shared methyl groups bridge between the two aluminium atoms. The Al-C(terminal) and Al-C(bridging) distances are 1.97 and 2.14 Å, respectively. The carbon atoms of the bridging methyl groups are each surrounded by five neighbors: three hydrogen atoms and two aluminium atoms. The methyl groups interchange readily intramolecularly and intermolecularly.

3-Centered-2-electron bonds are an utterance of "electron-deficient" molecules and tend to undergo reactions with Lewis bases that would give products consisting of 2-centered-2-electron bonds. For example, upon treatment with amines gives adducts R3N-AlMe3. Another reaction that gives products that follow the octet rule is the reaction of Al2Me6 with aluminium trichloride to give (AlMe2Cl)2.

The monomer species AlMe3, which has an aluminium atom bonded to three methyl groups, occurs at high temperature and low pressure.VSEPR Theory predicts and electron diffraction confirms that it has a trigonal planar (threefold) symmetry, as observed in BMe3.


...
Wikipedia

...