organoaluminium

Organoaluminium compounds are organometallic species that feature carbon–aluminium bonds. In these compounds aluminium is usually in the +3 oxidation state, and the aluminium center is typically three- or four-coordinate, giving tetrahedral or near-tetrahedral geometries in many alkylaluminium reagents. The most common members are trialkylaluminium compounds, such as trimethylaluminium (AlMe3) and triethylaluminium (AlEt3). These reagents are typically highly reactive, and many are liquids at room temperature; several are pyrophoric and strictly air- and moisture-sensitive.

Preparation of organoaluminium compounds often involves alkylation of aluminum halides with organomagnesium reagents. For example, AlCl3 can react with alkylmagnesium halides (RMgX) to give AlR3 and MgCl2. Other routes include redistribution or reduction of aluminum halides or hydrides to generate specific R groups. Workups are performed under inert atmosphere to prevent spontaneous ignition or hydrolysis.

Reactivity and properties of organoaluminium compounds are defined by their electrophilic aluminium center and presence of Al–C bonds. They readily hydrolyze in air or water to form aluminium hydroxide and alkanes, and they can behave as strong alkylating agents and, in some cases, as reducing reagents. They also act as Lewis acids and participate in various transformations, including hydroalumination of alkynes to furnish vinyl aluminums and transmetalation reactions. In industry, trialkylaluminium compounds serve as important precursors and co-catalysts in olefin polymerization, particularly in systems based on Ziegler–Natta and metallocene catalysts.

Safety and handling are critical: due to their pyrophoric and moisture-sensitive nature, they are typically stored and used under inert atmosphere, with appropriate protective equipment.