The Crystal Structure of (−)D-Tris(trimethylenediamine)cobalt(III) Bromide Monohydrate

The structure of (−)D-[Co(tn)3]Br3·H2O (tn: H2N–CH2-CH2-CH2-NH2) has been solved by the heavy atom method and refined to R=0.11 by least-squares analysis based on 1845 threedimensional data. The substance crystallizes in the monoclinic space group P21 with unit cell dimensions: a=16.274, b=9.863, c=9.489 Å, β=126.4° and Z=2. The complex ion in the structure has approximately a three-fold axis of rotation. The three six-membered Co-tn rings are nearly identical and take chair form. The chelate ring is rather flattened out, owing to the strong H-H repulsion. The absolute configuration of (−)D-[Co(tn)3]3+ has been found to be the same as that of (+)D-[Co(en)3]3+.