Hydro-coupling of isocyanates promoted by 1,2-bis(arylimino)acenaphthene aluminum hydrides

Abstract

The interaction of aluminum hydrides [(dpp-bian)AlH₂] (1) and [(Ar^BIG-bian)AlH₂(THF)] (2) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene; Ar^BIG-bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) with isocyanates RNCO (R = Ph, Cy, 3,5-Cl₂Ph) proceeds via insertion of two molecules of isocyanates into each Al–H bond with the formation of unique Al carboxamides [(Ar-bian)Al{OC(H)N(R)C(NR)O}₂] (Ar = dpp, R = Ph, 3; Ar = Ar^BIG, R = Ph, 4; Ar = Ar^BIG, R = Cy, 5; Ar = Ar^BIG, R = 3,5-Cl₂C₆H₃, 6). In contrast, the reactions of 1 and 2 with an excess of tert-butylisocyanate afford formimidate derivatives [(Ar-bian)Al{OC(H)N(tBu)}₂] (Ar = dpp, 7; Ar = Ar^BIG, 8). The reactions of N,N′-dicyclohexylcarbodiimide with 1 and 2 give [(dpp-bian)Al{(NCy)₂CH}₂] (9) and [(Ar^BIG-bian)Al(H){(NCy)₂CH}] (10), correspondingly. New compounds 3–10 have been characterized by ESR spectroscopy; their molecular structures have been established by single-crystal X-ray analysis.