Reactions of Carbon Dioxide Bound to Aluminum Diimine Hydride with Borane Dimethyl Sulfide and Ammonia

Abstract

The reaction of aluminum bis-formate acenaphthene-1,2-diimine complex [(Ar^BIG-bian)Al(μ-OC(H)O)₂Li(Thf)₂] (I) (Ar^BIG-bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene), prepared by binding carbon dioxide by aluminum diimine hydride [(Ar^BIG-bian)Al(H)₂]^–[Li(Thf)₄]⁺, with borane dimethyl sulfide and ammonia was studied. The reaction of I with BH₃∙SMe₂ (1 : 1) in toluene affords the product of hydroboration of one formate group [(Ar^BIG-bian)Al(μ-OC(H)O)(OB(H)OCH₃)Li(Thf)]₂ (II), while the reaction of I with BH₃∙SMe₂ (1 : 2) is accompanied by reduction of both formate groups and gives complex [(Ar^BIG-bian)Al(OBOCH₃)₂OLi₂(Thf)₂BH₄]₂ (III), methoxyboroxine (CH₃OBO)₃ and, presumably, compound [(Ar^BIG-bian)AlOCH₃]. The reaction of I with one equivalent of ammonia in THF gives adduct [(Ar^BIG-bian)Al(NH₃)(μ-OC(H)O)₂Li(Thf)₂] (IV), in which ammonia is coordinated to the aluminum atom, while the key bonds in I have not undergone ammonolysis. Compounds II–IV were characterized by IR and NMR spectroscopy, elemental analysis, and X-ray diffraction (CCDC no. 2255017 (II), 2255018 (III), 2255019 (IV)).