Reactivity of an aluminum hydride complex with a redox-active diimine ligand

Abstract

The reaction of the hydride [(dpp-bian)Al(H)Cl] (1) containing the 1,2-bis[(2,6-diisopropylphenyl) imino]acenaphthene (dpp-bian) radical anion with MeLi affords the compound [(dpp-bian)Al(H)Me] (2). The reaction of complex 1 with two equivalents of PhC≡CNa involves the replacement of chlorine along with oxidative substitution of hydrogen accompanied by the reduction of dpp-bian to the dianion to form the compound [(dpp-bian)Al(C≡CPh)₂Na(Et₂O)₂] ({sn3}). This reaction gives the complex [{dpp-bian(H)}Al(C≡CPh)₃Na(Et₂O)₂] (4) as the second product, which is apparently generated in the reaction of compound 3 with PhC≡CH. The reaction of compound 1 with Cp*Na (Cp* is pentamethylcyclopentadiene) in dimethoxyethane is also accompanied by the reduction of redox-active dpp-bian to the dianion, giving the complex [(dpp-bian)Al(H)Cl][Na(DME)₃] (5). Diamagnetic derivatives 3–5 were characterized by ¹H NMR spectroscopy; paramagnetic compound 2, by EPR spectroscopy. The molecular structures of compounds 2–5 were determined by X-ray diffraction.