Hydrogen-bonded and π-interaction assembly in two 8-alkoxycarbonyl-1,8-diazabicyclo[5.4.0]undec-7-enium chloride salts.

The crystal structures of 8-phen­oxy­carbonyl-1,8-diaza­bicyclo­[5.4.0]undec-7-enium chloride, C16H21N2O2+·Cl−, (I), and 8-meth­oxy­carbonyl-1,8-diaza­bicyclo­[5.4.0]undec-7-enium chloride monohydrate, C11H19N2O2+·Cl−·H2O, (II), recently reported by Carafa, Mesto & Quaranta [Eur. J. Org. Chem. (2011), pp. 2458–2465], are analysed and discussed with a focus on crystal inter­action assembly. Both compounds crystallize in the space group P21/c. The crystal packings are characterized by dimers linked through π–π stacking inter­actions and inter­molecular nonclassical hydrogen bonds, respectively. Additional inter­molecular C—H⋯Cl inter­actions [in (I) and (II)] and classical O—H⋯Cl hydrogen bonds [in (II)] are also evident and contribute to generating three-dimensional hydrogen-bonded networks.