A Saturated Heterocycle Formed from Ethane-1,2-diamine, Formaldehyde and Nitroethane: Crystal Structure of 6-Methyl-6-nitro-1,4-bis(2′-nitropropan-1′-yl)-1,4-diazacycloheptane

Abstract

The substituted saturated seven-membered heterocycle 6-methyl-6-nitro-1,4-bis(2′-nitropropan-1′-yl)- 1,4-diazacycloheptane crystallizes readily as a product from the reaction between [Re(en)₂O₂]⁺ (en = ethane-1,2-diamine), formaldehyde and nitroethane in basic solution. The complex apparently acts as a ‘molecular tap’, releasing en very slowly for reaction and favouring formation of discrete molecules rather than polymers, which form when free en alone is employed in the presence or absence of perrhenate ion. The trinitro cycloalkane crystallizes in the space group Pbca, with a 11·131(2), b 14·919(3), c 20·662(4) Å. A-CH₂-C(CH₃)(NO₂)-CH₂- chain links the two original primary amines of the ethane-1,2-diamine, in the same way that this type of chain links two primary amines of different ethane-1,2-diamine molecules in related metal-directed reactions. Further condensation involving the two secondary amines in the heterocycle intermediate leads to two -CH₂-CH(NO₂)-CH₃ pendants being formed, the relatively insoluble final product crystallizing readily from aqueous solution.