Aspects of the Chemical Energetics of Carbon–Aluminum Bonded Species

The current chapter discusses the chemical energetics of carbon-aluminum bonded species, both the “conventional” trivalent organoaluminum compounds such as monomeric Me3Al and its dimer and a variety of species of often surprising stoichiometry and structure. The study begins with the “simple” binary aluminum carbides, starting with AlC (neutral and ions). Incorporation of hydrogen leads to consideration of dimethylaluminum ionic compounds derived from the cationic [Me2Al]+ and anionic [Me2AlO]−. Methyldialuminum species with one Al–Al bond and at least one Al–C bond, ranging from [Al2Me]+ to [Al2Me7]−, are then examined. The experimental enthalpies of formation, vaporization and dimerization of trialkylalanes are tabulated. The most recent enthalpy of formation value for Et3Al is used to recommend slightly revised enthalpies of formation for trialkylalanes and the related alkylaluminum hydrides and halides. The interplay of aluminum and aromaticity is reviewed in the context of aluminum rich rings and clusters, relatively classical heterocycles such as aluminoles, and binding of neutral and cationic monoatomic Al with aromatics. The chapter closes with a discussion of aluminum halide complexes of benzene and cyclobutadiene derivatives. Keywords: aluminum carbide; trivalent organoaluminum compounds; monomers; dimers; neutral and related ions; dimethylaluminum species; methyldialuminum species; enthalpies of formation; enthalpies of vaporization; enthalpies of dimerization; alkylaluminum hydrides; alkylaluminum halides; aromaticity, rings and clusters; classical heterocycles; aluminum halide complexes