Reactions of an Aluminum Amide with Aromatic Nitriles: Formation of Al−N−C Frameworks

Reactions of a four-membered Al−N ring, [(Dipp)HNAlMe2]2 (2; Dipp =2,6-diisopropylphenyl), with the aromatic nitriles PhCN, TbpCN (Tbp =4-tert-butylphenyl), DmpCN (Dmp = 2,6-dimethylphenyl), DepCN (DepCN = 2,6-diethylphenyl), and DippCN are reported. 2 reacts with PhCN to give a 1:2 insertion product, the tetrameric aluminum amidinate 3, whereas with TbpCN it gives the 1:1 insertion products 4−6. Under similar conditions, DmpCN, DepCN, and DippCN do not undergo insertion but form simple adducts of alumazene (1), 7a−c and 8a−c (2:1 and 1:1 nitrile/alumazene), in which the nitriles coordinate to Al. Compounds 3−6 and 7a−c have been structurally characterized. 3 is comprised of four four-membered aluminum amidinate rings. 5 features a core made of three Al2N2 and two AlCN2 four-membered rings fused together. The structures of 4 and 6 consist of a dimer of a six-membered Al2CN3 framework. A high-yield synthesis of 3 from N-(Dipp)benzamidine and AlMe3 has also been reported.