229. Die Struktur der Hydrate von CO,[CO(CN),]~ und Cd,[Co(CN),],
von A. Ludi u n d H. U. Giidel Institut fur anorganischc, analytische und physikalische Cheinie dcr Universitat Bern, Freiestr. 3, CII-3000 Bern (14. X. 68) Summary. The crystal structures of Co,[Co(CN),],, 12 H,O (a = 10.210 & 0.005 A) and Cd,[Co(CN),],, 12 H,O (a = 10.590 & 0.005 A) have been determined b y X-ray powder methods. According t o the measured density the unit cell contains 11/, formula units with 4 Co2+ (Cda+) in 4a. Z2/, Co3+ in 4 b , 16 C and 16 N in 24e, 8 H,OI near 24e (96k) and 8 H,OrI near 8c (1921). Structure factor calculations based on the space group 02-F m 3 m lead to the following final values of the reliability index R : 0.038 (Co,[Co(CN),],, 1 2 H,O) and 0.037 (Cd,[Co(CN),],, 12 H,O).
The interatomic distances for the cobaltous compound (in parentheses €or thc cadmium compound) are: Co3+-C: 1.88 A (1.89); C-N: 1.15 -4 (1.17); Co2+-N: 2.08 A (2.24); Co2+-OI: 2.10 .
& (2.27);
shortest OI-H-OII-bonds : 2.89 A (2.82). Co3~k is octahedrally coordinated b y six carbon atoms, the divalent metal ion b y four nitrogen atoms and two watcr molecules. The two different metal ions are connected b y M2+-N-C-Co3+-bonds t o a threedimensional network. The infrared and electronic spectra are shown to be in agreement with the results of the structure analyses of these compounds. The observed positions of the OH-stretching vibrations lead to a hydrogenbond-length of 2.8-2.95 A.