ISSN:
1572-9001
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The title compound, [cis-Co(en)2(NO2)2](NO2) (1), crystallizes in the polar, nonenantiomorphic, monoclinic space group, Cc, with lattice constants:a=9.198(2) Å,b=12.444(2),c=9.963(3), andβ=96.76(2)°;V=1132.39 Å3 andd(calc;Z=4) =1.860 g cm−3. Thus, with NO2− as the counteranion, [cis-Co(en)2(NO2)2] crystallizes in a heterochiral lattice containing racemic pairs of cations. A total of 2699 data were collected over the range of 4°≤2θ≤70°; of these, 1859 (independent and withI≥3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ=15.465 cm−1) and the relative transmission coefficients ranged from 0.9934 to 0.7112. Refinement was carried out for both lattice polarities and the finalR(F) andR w (F) residuals were, respectively, 0.0242 and 0.0202 for (−−−) and 0.0264 and 0.0243 for (+++). Thus, the former was selected as correct for our specimen. Unlike all previous X-ray diffraction studies of the structural properties of the cation [cis-Co(en)2(NO2)2]+, which are found to have a pair of oppositely configured en rings [i.e., Δ(λδ) or Λ(λδ)], we find that in1 the cations are in the lowest energy conformation and configuration; i.e., Δ(λλ) or Λ(δδ). We attribute this change in configuration to the formation of strong interionic hydrogen bonds between nitrite anion oxygens and the axial—NH2 hydrogens, which markedly weaken the intermolecular and intramolecular hydrogen bonds between ligand—NO2 oxygens and the hydrogens of those same amine moieties. Thus, the nitrite anions behave exactly as nitrate anions, except that the hydrogen bonds found here are stronger than those formed by the latter. This is as expected since the negative charge is delocalized over two, instead of three, oxygens.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01374483
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