A Stable Neutral Radical in the Coordination Sphere of Aluminum

Abstract

Abstract The neutral radical (Me 2 ‐cAAC) 2 AlCl 2 ( 2 ) is stabilized by cyclic (alkyl)(amino)carbenes (cAACs). Complex 2 was synthesized by reduction of the Me 2 ‐cAAC:→AlCl 3 ( 1 ) adduct with KC 8 in the presence of another equivalent of Me 2 ‐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.