STRUCTURES WITH IDENTICAL PACKING - RACEMIC AND PARTIALLY OPTICALLY PURE 3-(2'-CHLORO-2'-PHENYLETHYL)-2-THIAZOLIDINIMINIUM P-TOLUENESULFONATE AND A COMPARISON OF THE PACKING IN CORRESPONDING RACEMIC AND OPTICALLY-ACTIVE COMPOUNDS

The crystal structures have been determined for racemic and two optica lly active samples of 3-(2'-chloro-2'-phenylethyl)-2-thiazolidiniminiu m p-toluenesulfonate (C11H14ClN2S+.C7H7O3S-) from low-temperature (122 K) X-ray diffraction data. The three crystal structures are virtually identical. The racemate crystallizes in the space group P2(1)/n, Z = 4, with unit-cell dimensions a = 8.5016 (10), b = 8.2803 (11), 27.447 (3) Angstrom and beta = 96.478 (9)degrees. The cation displays disorde r of the CI atom and the C atom to which it is bonded. The disorder ca n be rationalized in terms of the presence of two partially populated enantiomers with different conformations. The two optically active sal ts contain both enantiomers of the chiral cation. The ratios between t he R-and S-enantiomers were estimated to be 0.944 (7)/0.056 (7) and 0. 860 (7)/0.140 (7). Both salts crystallize in the space group P2(1) wit h unit-cell dimensions almost identical to those of the racemate. The two independent anions and the ring systems of the cations are related by pseudoinversion symmetry. One of the independent cations has a dis order similar to that found for the racemate. The system of hydrogen b onds connecting two cations and two anions into 12-membered rings is i dentical in the racemic and in the optically active crystals. Addition al evidence for the formation of a solid solution between the enantiom ers and the racemate is provided by thermoanalytical and IR measuremen ts. The crystal structures of 64 pairs of racemate and its correspondi ng enantiomer have been analysed. Relations similar to that observed f or the salts in the present study were found for six of the pairs. For another eight pairs, there is a great resemblance between the packing of the racemate and the corresponding enantiomers.