Al–Sc Bonded Complexes: Synthesis, Structure, and Reaction with Benzene in the Presence of Alkyl Halide

An alumanyl anion possessing N,N′-bis(2,6-diisopropylphenyl)-1,3-propanediamine ligand was synthesized and characterized. Transmetalation of this Al anion with diaminoscandium chloride precursors afforded the corresponding Al–Sc complexes possessing an unprecedented Al–Sc bond. The Al–Sc[N(SiMe3)2] complex underwent intramolecular C–H cleavage to form a bridged dinuclear complex with μ-hydrido and μ-methylene ligands. The Al–Sc(NiPr2)2 complex reacted with benzene in the presence of alkyl bromide to furnish a 1,4-dialuminated cyclohexadiene product with a concomitant formation of the alkyl–alkyl coupled product. Although the latter product seems to form through the radical mechanism, DFT calculations revealed an ionic mechanism involving bimetallic reaction pathways to react with alkyl bromide and benzene, which provides new insight into the chemistry of metal–metal bonded compounds.