The phenomenon of conglomerate crystallization in coordination compounds. XXIII: The crystallization behavior of [cis-Co(en)2(N3)(SO3)] � 2H2O (I) and of [cis-Co(en)2(NO2)(SO3)] � H2O (II)

Abstract

A room temperature water solution of (I) crystallizes as a racemate, space groupP21/n with lattice constantsa=7.737(6),b=10.694(5),c=15.097(6) A, andβ=102.83(5)°;V=1218.05 A3 andd (calc; M.W.=337.24, Z=4) = 1.642 g cm−3. A total of 2381 data were collected over the range 4° ≤ 2θ < 50°; of these, 1452 (independent and withI ≥ 3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ = 15.76 cm−1), and the relative transmission coefficients ranged from 0.8976 to 0.9984. Refinement led to the finalR(F) andRw(F) residuals of 0.0858 and 0.1116. A room temperature water solution of (II) crystallizes as a racemate in space group P21/c with lattice constantsa=6.638(3),b=11.425(8),c=15.147(16) A, andβ=93.27(6)°; F=1146.8 A andd (calc; M.W.=323.2,Z=4) = 1.872 g cm−3. A total of 2200 data were collected over the range 4° ≤ 2θ < 50°; of these, 1918 (independent and withI ≥ 3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ=16.94 cm−1), and the relative transmission coefficients ranged from 0.9049 to 0.9967. Refinement led to the finalR(F) andRw(F) residuals of 0.0231 and 0.0279. The chirality symbol for the particular enantiomer of (I) refined here is ∧ (δδ), while for (II) the chirality symbol is ∧(δλ), which means that in the latter compound one of the en rings is in a higher energy conformation. We attribute this result to competitive intramolecular hydrogen-bonded interactions between the — NH2 hydrogens of the en ligands and the oxygens of the -NO2 and -SO3 ligands, strengths which are enhanced by coercing a change in sign of the torsional angle of one en ringa motion which permits both oxo ligands to form stronger hydrogen bonds while retaining proper O ⋯ O contacts. This phenomenon is not observed in (I) since the azide ligand does not compete with -SO3 for such hydrogen-bonded interactions, and nonbonded pair repulsions can be minimized without affecting the ability of — SO3 oxygens to form strong intramolecular hydrogen bonds.