Triethylaluminium
Triethylaluminium is one of the simplest examples of an organoaluminium compound. Despite its name it has the formula Al(CH) (abbreviated as AlEt or TEA), as it exists as a dimer. This colorless liquid is pyrophoric. It is an industrially important compound, closely related to trimethylaluminium. Structure and bonding. The structure and bonding in AlR and diborane are analogous (R = alkyl). Referring to AlMe, the Al-C(terminal) and Al-C(bridging) distances are 1.97 and 2.14 Å, respectively. The Al center is tetrahedral. The carbon atoms of the bridging ethyl groups are each surrounded by five neighbors: carbon, two hydrogen  atoms and two aluminium atoms. The ethyl groups interchange readily intramolecularly. At higher temperatures, the dimer cracks into monomeric AlEt. Synthesis and reactions. Triethylaluminium can be formed via several routes. The discovery of an efficient route was a significant technological achievement. The multistep process uses aluminium metal, hydrogen gas, and ethylene, summarized as follows: Because of this efficient synthesis, triethylaluminium is one of the most available organoaluminium compounds. Triethylaluminium can also be generated from ethylaluminium sesquichloride (AlClEt), which arises by treating aluminium powder with chloroethane. Reduction of ethylaluminium sesquichloride with an alkali metal such as sodium gives triethylaluminium: Reactivity. The  Al–C bonds of triethylaluminium are polarized to such an extent that the carbon is easily protonated, releasing ethane: For this reaction, even weak acids can be employed such as terminal acetylenes and alcohols. The linkage between the pair of aluminium centres is relatively weak and can be cleaved by Lewis bases (L) to give adducts with the formula AlEtL: Applications. Precursors to fatty alcohols. Triethylaluminium is used industrially as an intermediate in the production of fatty alcohols, which are converted to detergents. The first step involves the oligomerization of ethylene by the "Aufbau" reaction, which gives a mixture of  trialkylaluminium compounds (simplified here as octyl groups): Subsequently, these trialkyl compounds are oxidized to aluminium alkoxides, which are then hydrolysed: Co-catalysts in olefin polymerization. A large amount of TEAL and related aluminium alkyls are used in Ziegler-Natta catalysis. They serve to activate the transition metal catalyst both as a reducing agent and an alkylating agent. TEAL also functions to scavenge water and oxygen. Reagent in organic and organometallic chemistry. Triethylaluminium has niche uses as a precursor to other organoaluminium compounds, such as diethylaluminium cyanide: