Studies in X-ray Crystallography : I. Calcium Chloride Hexahydrate. II. Hexamethylene Tetramine Complexes with Metal Halides

I. The crystal structure of calcium chloride hexahydrate has been determined by means of Patterson syntheses and stereochemical consideration of the atomic positions allowed by possible space groups. The parameters were determined from peaks in the Patterson syntheses, which were well resolved. This determination confirms the conclusions of Jensen (7,8), who used a method of successive Fourier syntheses to arrive at the structure of the alkaline earth hexahydrates and to obtain approximate parameters for strontium chloride hexahydrate, but did not refine these parameters. The results of this investigation were as follows: Space group: D23-C321 Unit cell: a = 7.80 Å., c = 3.95 Å.; contains one molecule CaCl2·6H2O. Atomic positions: Ca at 1(a) 0 0 0; Cl at 2(d) ⅓ ⅔ z, ⅔ ⅓ z, z = 0.576 0I at 3(e) x 00, 0 x 0, x x 0, x = 0.313 0II at 3 (f) x 0 ½ , 0 x ½, x x ½, x = -0.218 The bonding within the crystal is discussed in the light of the observed interatomic distances. II. The structures of certain complexes of metal halides with hexamethylene tetramine, C6H12N4, have been investigated. The compound SnCl4·4C6H12N4 and the isomorphous TiCl4·4C6H12N4 have space group C53v-R3m. The triply primitive hexagonal unit cell has a = c = 8.95 Å. It contains three hexamethylene tetramine molecules and three chlorine atoms. The centers of the hexamethylene tetramines and of the chlorines form two interpenetrating rhombohedral lattices, separated by half the rhombohedral body diagonal. The tin atoms are probably distributed randomly among the gaps between the larger atoms. the compounds MnCl2·2C6H12N4 and 2·2C6H12N4 give powder photographs considerably different from each other. The former has Laue symmetry D2h, a = 11.86 Å., b = 21.92 Å., c = 7.23 Å. The lattice is primitive. There is no glide plane normal to a, but possibly an n glide normal to b and probably a b glide normal to c. A complex of hexamethylene tetramine with SnCl2 gave the same powder pattern as SnCl4·4C6H12N4. A compound with SbCl3 gave the same pattern with a few additional lines. The formulas of the complexes are reported (7) to be SnCl2·2C6H12N4 and SbCl3·3C6H12N4. The main factors determining the structures of these compounds seem to be packing of the anions with hexamethylene tetramine molecules and interactions among the letter as in crystals of the pure compound .