Aluminum hydrides with radical-anionic and dianionic acenaphthene-1,2-diimine ligands

Abstract

The reaction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with LiAlH₄ affords two products regardless of the solvent used (tetrahydrofuran or diethyl ether). These products were isolated as green and colorless crystals. Green crystals of the complex [(dpp-bian)Al(H)₂Li(THF)₃] (1) were obtained from tetrahydrofuran; colorless crystals of the complex [{dpp-bian(H₂)}Al(H)₂Li(Et₂O)₂] (2), from diethyl ether. The reactions of compound 1 with 2,6-di-tert-butyl-4-methylphenol and benzophenone gave monohydrides [(dpp-bian)Al(H)(OC₆H₂-2,6-Bu₂^t-4-Me)][Li(THF)₄] (3) and [(dpp-bian)Al(H)(OCHPh₂)- Li(THF)₂] (4), respectively. The diamagnetic aluminum hydride [(dpp-bian)AlH(THF)] (5) was synthesized by the reaction of dichloroalane HAlCl₂ (in situ) with the disodium salt of dpp-bian in THF; the paramagnetic hydride [(dpp-bian)AlH(Cl)] (6) containing the dpp-bian radical anion was synthesized by the reaction of the monosodium salt (dpp-bian)Na with monochloroalane H₂AlCl (in situ) in diethyl ether. The reaction of compound 6 with tert-butyllithium gives the complex [(dpp-bian)AlBu^t(Et₂O)] (7). Diamagnetic derivatives 1—5 and 7 were characterized by ¹Н NMR spectroscopy; paramagnetic compound 6, by ESR spectroscopy. The molecular structures of compounds 1—7 were determined by single-crystal X-ray diffraction.