Aluminium alkylaluminium halides

Organometallics can be prepared by anodic generation of reactive metal ions. Alkylaluminium halides, R-A1-X2, are produced by electrolysis of alkyl halides in the presence of AIX3 at an aluminium anode. AlX is assumed to be the reactive intermediate, which inserts into the C—Hal bond to form product (Eq. (276) ). 

While investigating the oligomerization of ethene by aluminium alkyls (p. 80), Ziegler and coworkers noticed that in the presence of traces of nickel dimerization to 1-butene occurs instead. Very active catalysts can be generated by adding an alkylaluminium halide to [(f/ -CjHJNiCl]. The phosphine complexes NiL are also effective in the presence of acids. A nickel hydrido complex is first formed which adds to ethene to give an ethyl intermediate which can either eliminate 1-... 

Three main structural sub-groups can be recognised alkylaluminium dihalides, dialkylaluminium halides, and trialkyldialuminium trihalides (equimolar complexes of a trialkylaluminium and an aluminium trihalide). While this is generally a very reactive group of compounds, similar in reactivity to trialkylaluminium compounds, increase in size of the alkyl groups present and in the degree of halogen substitution tends to reduce pyrophoricity. 

With suitable halides, aluminium gives alkylaluminium sesquihalides ... 

This reaction is very limited in scope, but gives some useful products. It works well with methyl and ethyl halides, the chlorides being much the most important as they are so much cheaper than bromides and iodides. Aluminium generally needs activating, and one of the most effective ways is by means of some preformed alkylaluminium compound, though iodine or AICI3 can also be used. Phenylaluminium sesquichloride is formed, only with difficulty, when PhQ reacts with aluminium which has been... 

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