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.