8,11-Diaza[4.3.3]propell-6-enium oxalate 2.5 hydrate

The diaza[4.3.3]-propell-6-enium cation has a staggered conformation, in ac cordance with earlier work which suggested that staggered conformations of [4.3.3]propellenes are about twice as frequent as eclipsed conformations. T he conformations of the three rings have been analyzed using the methods of Boeyens and Evans. Although the oxalate anion would be expected formally t o have four equivalent C-O bonds, the dimensions found show only two equiva lent C-O bonds, with the other two approximating to a double and a single b ond respectively. This suggests that the structure is actually close to tha t of a hydrogen oxalate anion. This situation appears to arise from the str ong, symmetrical hydrogen bond that links two oxalate anions. The water mol ecules are disordered in channels between the linked cation-anion sheets. V arious possibilities are advanced for the manner in which charge balance is achieved by proton transfer.