The neutral radical (Me2 -cAAC)2 AlCl2 (2) is stabilized by cyclic (alkyl)(amino)carbenes (cAACs). Complex 2 was synthesized by reduction of the Me2 -cAAC:→AlCl3 (1) adduct with KC8 in the presence of another equivalent of Me2 -cAAC. The crystal structure of 2 shows that the Al-C bond lengths of the two carbenes bound to the Al center are considerably different, which is likely the result of intermolecular interactions. Quantum-chemical calculations from the gas phase give an equilibrium structure with identical Al-C bond lengths. Compound 2 exhibits monoradical character, which was confirmed by EPR measurements. A bonding analysis indicates that the unpaired electron resides mainly at the carbene carbon atoms. Compound 2 is an example for an unusual neutral Al radical.
Keywords: aluminum radicals; bonding analysis; cyclic alkyl(amino) carbenes; theoretical calculations.
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