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.合成并表征了一种由N,N′-双(2,6-二异丙基苯基)-1,3-丙二胺配体配位的铝基阴离子（alumanyl anion）。该铝阴离子与二氨基氯化钪前驱体发生转金属化反应（transmetalation），得到了带有前所未有的Al-Sc键的相应Al-Sc双金属配合物。其中Al-Sc[N(三甲基硅基)₂]配合物发生分子内C-H键断裂，生成了带有μ-氢配体和μ-亚甲基配体的桥联双核配合物。Al-Sc(二异丙基氨基)₂配合物在烷基溴存在下与苯反应，生成1,4-二铝代环己二烯产物，同时伴随烷基-烷基偶联产物的生成。尽管后一产物看似通过自由基机理形成，但密度泛函理论（DFT, Density Functional Theory）计算结果表明，该反应实际通过涉及双金属反应路径的离子机理与烷基溴和苯发生反应，这为金属-金属键合化合物的化学研究提供了全新的视角。