Synthesis and X-ray crystallographic characterization of substituted aryl imines

We report the synthesis of α-diimine 1,4-bis(2,5-di-tert-butylphenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene, 1, and α-iminoketones 2-[(3,5-xylyl)imino]acenaphthylen-1-one, 4, and 2-[(4-chlorophenyl)imino]acenaphthylen-1-one, 5, all of which have been characterized by 1H NMR, 13C NMR, IR, and X-ray crystallography. Also, we report the previously unknown X-ray crystal structures of α-diimines Ar-BIAN (Ar-BIAN = bis(arylimino)acenaphthene; Ar = 3,5-xylyl, 2; Ar = 4-chlorophenyl, 3) and α-iminoketone 2-[(2,6-xylyl)imino]acenaphthylen-1-one, 6. In solution, 4 and 5 show fluxional behavior observed with variable temperature 1H NMR in DMSO-d6 which is attributed to isomerization between the E and Z form of the imine.