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 optically active samples of 3-(2'-chloro-2'-phenylethyl)-2-thiazolidiniminium 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 disorder of the CI atom and the C atom to which it is bonded. The disorder can be rationalized in terms of the presence of two partially populated enantiomers with different conformations. The two optically active salts contain both enantiomers of the chiral cation. The ratios between the 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) with 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 disorder similar to that found for the racemate. The system of hydrogen bonds connecting two cations and two anions into 12-membered rings is identical in the racemic and in the optically active crystals. Additional evidence for the formation of a solid solution between the enantiomers and the racemate is provided by thermoanalytical and IR measurements. The crystal structures of 64 pairs of racemate and its corresponding enantiomer have been analysed. Relations similar to that observed for 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.