The phenomenon of conglomerate crystallization. IX. Clavic dissymmetry in coordination compounds. VII. An investigation of the crystallization behaviour of [ trans-Co(en) 2(ONO)X]Y, [ trans-Co(en) 2(NO 2)X]Y, With (X = NO 2−, NCS −) and (Y = I −, ClO 4−, NO 3−, NCS −) and the crystal structures of racemic [ trans-Co(en) 2(NO 2) 2]I (VII) and of racemic [

Abstract

The compounds [ trans-Co(en) 2(NO 2) 2]X (X = I, NCS) will, hereafter, be referred to as VII and VIII. Compound VII crystallizes in space group C2/ c with cell constants a=10.743(2), b=9.179(3), c= 13.432(3) Å, β=112.28(2)°; V=1225.56 Å 3, d calc=2.157 g cm −3 and Z=4. Chemical formula for VII= C 4H 16N 6O 4CoI; M R = 398.05 and μ= 39.012 cm t̄1; absorption corrections were made and the relative values of the transmission coefficients were 99.96 to 77.38. Compound VIII crystallizes in the triclinic system, space group P 1 , a=6.496(2), b=9.192(3), c=10.956(8) Å, a=89.58(5)°, β= 79.70(5)°, γ=75.7t(2)°; V=623.26 Å 3, d calc= 1.754 g cm −3 and Z=2. Chemical formula for VIII = C 5H 16N 7O 4SCo; M R = 329.22, μ = 15.532 cm −1 and transmission coefficients ranged from 99.99 to 73.36. Total data collected for VII: 1238 of which 1048 were independent and had I> 3σ( I) and VIII: 3840 of which 657 were symmetry related forms which were averaged ( R=0.012). The remaining 3183 were above 3σ( I) and were, thus considered observed. Both structures were solved by Patterson methods and refined to R and R f factors of 0.0284 and 0.0350 for VII and 0.0216 and 0.0276 for VIII. Both molecules crystallize in centrosymmetric space groups. The cation of VII sits at a crystallographic inversion center while that of VIII is located at a general position; nonetheless, it has a nearly perfect, molecular, inversion center. In both compounds, the cations have a λ and a δ conformed ethylenediamine which in the case of VII is required by the inversion center. Comparison of the stereo- chemical parameters of the Co(en) 2 fragments in VII and VIII reveal them to be nearly identical. However, the −NO 2 ligands in VII are bent towards the terminal −NH 2 of the basal plane in what is, obviously, an attempt to form as strong NH···ON intramolecular hydrogen bonds as possible. This is not the case with the −NO 2 ligands of VIII which are almost exactly orthonormal to the CoN 4 base. This phenomenological difference in behaviour of the −NO 2 ligands is due to the difference in hydrogen bonding ability of the two compensating anions. Bond lengths and angles compare favorably with literature results on relevant substances.