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 b rethren, 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 w ith 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 ch loride 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), i n the solid state that of [cis-(-)589-Co(en)2(NO2)2]I (I) is LAMBDA(la mbdalambda). The cations of I form infinitely hydrogen-bonded, homochi ral, helical strings about the four-fold screw axis of the crystals. I n turn, adjacent helical strings are held together by hydrogen bonds b etween the iodides and -NH2 hydrogens of the amine ligands. Such an ar rangement is also present in the isomorphous chloride and bromide deri vatives; however, in those compounds the infinite spirals are wound ab out the two-fold screw axis of the space group P2(1).