Why are hexol cluster cations [tris(cis-tetraaminedihydroxo)Co](+6) so easily resolved into their antipodes? Part 2. Preparation, crystal structural studies and the nine sources of chirality of hexol clusters

Heretofore, it had been impossible to determine the structure of the origin al Werner's hexol cation inasmuch as the synthetic procedure given by Werne r produces crystals unsuitable for single crystal X-ray (XRD) diffraction s tudies. Thus, it was greatly satisfying that crystals obtained here, using a different method of preparation, produced useful crystals of three differ ent derivatives. X-ray quality crystals of composition [Co(NH3)(4)CO3][Co{( HO)(2)Co(NH3)(4)}(3)](NO3)(6)(OH) . 2 H2O(III) were obtained while attempti ng to grow crystals of [Co(NH3)(5)CO3]NO3 from water solutions allowed to e vaporate at room temperature (ca. 22 degreesC). (III) crystallizes in space group P (1) over bar (No. 2), with lattice constants: a = 11.767(1), b = 1 2.856(2), c = 17.040(1) Angstrom, alpha = 75.49(2), beta = 72.59(2), gamma = 68.53(7)degrees, V = 2259.84 Angstrom (3), and d (calc; M.W. = 1148.2, Z = 2) = 1.687 g-cm(-3). A total of 4428 data were collected using MoKalpha ( lambda = 0.71073 Angstrom radiation, over the range of 4 degrees less than or equal to 2 theta less than or equal to 40 degrees; of these, 2469 [indep endent and with I greater than or equal to 3 sigma (I)] were used in the st ructural analysis. Data were corrected for absorption (mu = 18.97 cm(-1)) a nd transmission coefficients ranged from 0.536 to 0.999. The final R(F) and R-W(F) residuals were, respectively, 0.18 and 0.18, the high values of whi ch are due to disorder of several of the nitrate counteranions. Nonetheless , the results are of interest since this double salt consists of two fully ordered cations: [Co(NH3)(4)CO3](+), containing a bidentate carbonate ligan d, and Werner's hexol cation {Co[Co(OH)(2)(NH3)(4)](3)}(6+). The presence o f the bidentate carbonate cation is important in view of the fact that the starting material was the monodentate pentaamine carbonate cation, a result which provides a guide to the mechanism of the reactions involved in the p reparation of compound (III), in particular, and of the hexol cations, in g eneral. Thus, this study is an amplification of our recent description [1] of Werner's hexol salts. Finally, we explain here the origin of the large o ptical rotatory power of these cations and enumerate the nine sources of ch irality present in them. in our previous paper, we listed only seven [1]; h owever, we have recently come to realize there are two additional ones, des cribed below.