Reactions of an Aluminum Amide with Aromatic Nitrites: 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 nitrites 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.