Chemistry of diaminomaleonitrile: synthesis and structure of two unexpected products from its condensation with 2,5-hexanedione

For the synthesis of precursors to cellulose-based ion exchange materials, the condensation of diaminomaleonitrile with 2,4-pentanedione and 2,5-hexanedione was explored. Whilst the former diketone yielded the expected 1,4-diazepine (2), the latter gave either a pyrrole derivative (3) or an unusual triazabicyclononene (4), depending on the conditions used. Compound 2 crystallizes in the monoclinic space group P2₁/c with a = 8.9313(10) Å, b = 9.0370(7) Å, c = 11.4448(9) Å, = 102.48(8)°, V = 901.89(14) ų, and Z = 4. Compound 3 crystallizes in the orthorhombic space group Pna2₁ with a = 12.0342(8) Å, b = 8.3760(8) Å, c = 10.7026(11) Å, V = 1078.81(17) ų, and Z = 4. Compound 4 crystallizes in the monoclinic space group P2₁/c with a = 9.0157(5) Å, b = 13.5374(9) Å, c = 12.8751(16) Å, = 99.506(5)°, V = 1549.82(15) ų, and Z = 4. In both 3 and 4 the aminovinyl substituent shows evidence for involvement of the lone pair on nitrogen with the carbon -system. Also, 3 and 4 are highly associated in the solid state via hydrogen bonding.