The crystallization behavior of (+)-cis-alpha-[Co(dmtrien)(NO2)(2)]Cl center dot 0.5H(2)O 1 and (+/-)-cis-alpha-[Co(dmtrien)(NO2)(2)]I 2 (dmtrien = 3,6-dimethyl-3,6-diazaoctane-1,8-diamine)

The compound (+/-)-cis-alpha-[Co(dmtrien)(NO2)(2)]Cl . 0.5H(2)O 1 has been found to crystallize as a kryptoracemate in the space group C2 (Z = 4) with a racemic pair as the asymmetric unit, whereas (+/-)-cis-alpha-[Co(dmtrien )(NO2)(2)]I 2 crystallizes as a simple racemate, as expected (dmtrien = 3,6 -dimethyl-3,6-diazaoctane-1,8-diamine For 1 the two cations in the asymmetr ic unit had the conformations Delta(lambda delta lambda), Co(1), and Lambda (delta lambda delta), Co(2), and those of the chiral, methylated, nitrogens of Co(1.) are (S,S) while those of Co(2) are (R,R). Compound 2 crystallize s as a racemate in the space group Peen (Z = 8); the anions are in a genera l position but there are two half cations sitting at two-fold axes of the s pace group. For 1, Co(1) and Co(2) cations form separate spiral strings whi ch extend through the length of the a axis, and these strings are held toge ther by hydrogen bonds to the anions and waters of crystallization. Each st ring contains, exclusively, cations of single chirality and layers of homoc hiral strings define the ab plane of the crystals. Each layer is of opposit e chirality to the pair of adjacent ones. In 2 the packing is different in that there are strings made exclusively of either Co(1) or Co(2) running al ong the diagonal of the be plane, as well as [-Co(1)-Co(2)Co(1)Co(2)-](n).. . strings running parallel to the c axis.