Concomitant polymorphism: Crystallising dichloro-bis(2,4-lutidine)-zinc as both chiral and racemic phases

The crystallisation of dichloro-bis(2,4-lutidine)-zinc from various solvents (e.g. ethanol, THF and 2,4-lutidine) has been investigated and two phases were isolated. The structures of both phases were determined by single crystal X-ray diffraction and both types of crystals were found to be composed of conformationally chiral molecules. One phase (α-1) is racemic and crystallises in space group P21/c, while the other phase (β-1) crystallises in the enantiomorphous space group P41212 with a low Flack parameter. In a few cases the chiral and racemic phases crystallised concomitantly; this phenomenon is rare and can be useful in the development of tools for the prediction of crystal structures.