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

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