Mixed Lithium–Aluminum Hydrides Bearing Ar-Bian Ligands: Reactivity Toward Heteroallenes

The reactivity of [(dpp-Bian)Al(H)2Li(THF)3] (1) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and [(ArBIG-Bian)Al(H)2Li(THF)4] (2) (ArBIG-Bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) toward isocyanates and carbodiimides has been investigated. A treatment of 1with tert-buthylisocyanate affords the formimidate derivative [(dpp-Bian)Al(μ2-OC(H)NtBu)2Li(THF)] (3). The related [(ArBIG-Bian)Al(μ2-OC(H)NCy)2Li(THF)] (4) and [(ArBIG-Bian)Al((μ-OC(H)NPh)Li(THF)3)(OC(H)NPh)] (5) have been obtained by reacting of 2with cyclohexyl and phenylisocyanates, respectively. Cyclohexylcarbodiimide reacts with 1and 2to give the corresponding amidinate derivatives [(dpp-Bian)Al(CyNC(H)NCy)(μ-CyNC(H)NCy)Li(THF)2] (6) and [(ArBIG-Bian)Al(CyNC(H)NCy)][Li(DME)3] (7). Complexes 3-7were characterized by IR and NMR spectroscopy. The molecular structures of compounds 3-7were determined by single-crystal X-ray analysis. Both 1and 2serve well as catalysts in the hydroboration of isocyanates and carbodiimides by pinacolborane (HBpin).