Trimethylaluminum: Bonding by Charge and Current Topology.

The charge density distribution of the trimethylaluminum dimer was determined by high-angle X-ray diffraction of a single crystal and quantum-chemical methods and analyzed using the quantum theory of atoms in molecules. The data can be interpreted as Al2Me6 being predominantly ionically bonded, with clear indications of topological asymmetry for the bridging Al-C bonds owing to delocalized multicenter bonding. This interpretation is supported by the calculated magnetic response currents. The data shed new light on the bonding situation in this basic organometallic molecule, which was previously described by contradicting interpretations of bonding.