THE PHENOMENON OF CONGLOMERATE CRYSTALLIZATION .32. THE CRYSTALLIZATION BEHAVIOR OF [CIS-CO(EN)2(NO2)2]I .1. COUNTERION EFFECTS ON CRYSTALLIZATION PATHWAY OF RACEMATE SOLUTIONS .3.

[Cis-Co(en)2(NO2)2]I (I), ICoO4N6C4H16, crystallizes from water at 18-degrees-C as both a racemate and a conglomerate. The structure of the latter was determined in th's study. Unlike its chloride and bromide brethren, which crystallize exclusively as conglomerates, in the space group P2(1), the iodide crystallizes in the tetragonal space group P4(1) (No. 76). The absolute configuration was determined by comparison with that of the parent compound, (-)589-[LAMBDA(deltalambda)-cis-Co(en)2(NO2)2]Br (III), from which it was made by metathesis. Unlike the chloride and parent bromide, whose chiroptical symbols are Co(en)2(NO2)2]Cl (II) and [cis-(-)589-LAMBDA(deltalambda)-Co(en)2(NO2)2]Br (III), in the solid state that of [cis-(-)589-Co(en)2(NO2)2]I (I) is LAMBDA(lambdalambda). The cations of I form infinitely hydrogen-bonded, homochiral, helical strings about the four-fold screw axis of the crystals. In turn, adjacent helical strings are held together by hydrogen bonds between the iodides and -NH2 hydrogens of the amine ligands. Such an arrangement is also present in the isomorphous chloride and bromide derivatives; however, in those compounds the infinite spirals are wound about the two-fold screw axis of the space group P2(1).