The phenomenon of conglomerate crystallization .48. Two polymorphs of racemic trans-[CO(2,3,2-tet) (NO2)(2)]NO3 (I and II)

A racemic solution of trans-[Co(2,3,2-tet)(NO2)(2)]NO3(I), CoO7N7C7H20, crystallizes as a racemate in the centrosymmetric space group, P2(1)/n with lattice constants: a = 8.490(2) Angstrom, b = 8.884(2), c = 18.580(2) Angstrom and beta = 95.08(1)degrees; V = 1395.89 Angstrom(3) and d(calc; M.W. = 373.21, Z = 4) = 1.776 g-cm(3). A total of 3489 data were collected over the range of 4 degrees less than or equal to 2 theta less than or equal to 55 theta; of these, 2684 (independent and with 1 greater than or equal to 3s(I)) were used in the structural analysis. Data were corrected for absorption (mu = 12.732 cm(-1)) and the relative transmission coefficients ranged from 0.7721 to 0.9980. Refinement converged to final residuals of 0.0465 and 0.0541 for R(F) and R-W(F), respectively. The mother liquor of the same compound, prepared by a different route, produced a second crystalline form of trans-[Co(2,3,2-tet)(NO2)(2)]NO3(II), CoO7N7C7H20, which crystallizes in space group Pn with lattice constants: a = 6.493(5)Angstrom, b = 11.731(4), c = 9.325(4) Angstrom and b = 100.13(9)degrees; V = 699.21 Angstrom(3) and d(calc; M.W. = 373.21, Z = 2) = 1.773 g-cm(-3). A total of 2249 data were collected over the range of 4 degrees less than or equal to 2 theta less than or equal to 60 degrees; of these, 2012 (independent and with I greater than or equal to 2.5s(I)) were used in the structural analysis. Data were corrected for absorption (mu = 12.732 cm(-1)) and the relative transmission coefficients ranged from 0.7892 to 0.9345. Refinement converged to final residuals of 0.0301 and 0.0308 for R(F) and R-W(F), respectively. For (I) and (II), the central six-membered ring has a chair conformation. The conformational chirality of the two five-membered, outer rings and the asymmetry at the secondary nitrogens, are internally compensated(meso) and, with the exception of small deviations at the -NO2 oxygens, the cation has a mirror plane which bisects the central ring. In both cases the asymmetric unit is an ion pair in which nitrate oxygens form bonds with the hydrogens of both terminal -NH2 moieties-the entire array resembling a macrocycle. The composition of both crystals is identical but while the lattice of both crystals contain racemic pairs, (I) is centrosymmetric, while crystals of (II) are polar.