Kryptoracemic crystallization .4. Synthesis and X-ray structure of the conglomerate [Co(en)(2)Ox]F center dot 11.5H(2)O(I), another example of a coordination compound crystallizing as a kryptoracemate

A racemic solution of [Co(en)(2)Ox]F.11.5H(2)O(I), CoFO15.5N(4)C(6)H(39), crystallizes as a kryptoracemate in the enantiomorphic space group C2 (No. 5) with lattice constants: n = 21.150(19) Angstrom, b = 11.866(8), c=13.197(2) Angstrom and beta = 101.62(8)degrees; V = 3243.97 Angstrom(3) and d(calc; M.W.= 493.92 gm-mol(-1), z = 8)= 2.020 g-cm(-3) A total of 2335 data were collected over the range of 4 degrees less than or equal to 2 theta less than or equal to 45 degrees; of these, 1735 (independent and with I greater than or equal to 2.5 sigma(I)) were used in the structural analysis. Data were corrected for absorption (mu=10.75 cm(-1)) and the relative transmission coefficients ranged from 0.5557 to 0.7852. Refinement converged to final residuals of 0.063 and 0.072 for R(F) and R-W(F), respectively. There are two formula weights in the asymmetric unit of (I) and the absolute configuration was determined by the Flack test. For (I), the absolute configuration at Co1 is Lambda(delta lambda) and for Co2 is Delta(lambda delta), which by comparison with the known absolute configurations of the chloride and bromide derivatives,(4) allows us to assign the full chiro-optical symbol for these cations. Thus, the cations present in the crystal selected for the structural study of (I) are characterized fully by the symbols (+)589-Lambda(delta lambda)-[Co1(en)(2)Ox]F.11.5H(2)O and (-)589-Delta(lambda delta)-[Co-2(en)(2)Ox]F.11.5H(2)O. The two cations are located near a non-crystallographic, pseudo-inversion center located approximately at 1/4, 0, 1/4, as determined from the positions of the two independent Co atoms; however, this pseudo-inversion center is only approximately shared by the four nitrogens and two oxygens in the coordination sphere, and is seriously violated by the other atoms of the metal ligands. This is, to our knowledge, the first coordination compound of Co(III) which crystallizes, from a racemic solution, in an enantiomorphic lattice with a fluoride as its anion. Moreover, this is also the first fluoride to crystallize as a kryptoracemate.