Die Struktur der Hydrate von Co3[Co(CN)6]2 und Cd3[Co(CN)6]2

The crystal structures of Co3[Co(CN)6]2, 12 H2O (a, = 10.210 ± 0.005 Å) and Cd3[Co(CN)6]2, 12 H2O (a = 10.590 ± 0.005 Å) have been determined by X‐ray powder methods. According to the measured density the unit cell contains 1 1/3 formula units with 4 Co2+ (Cd2+) in 4a, 2 2/3 Co3+ in 4b, 16 C and 16 N in 24e, 8 H2OI near 24e, (96k) and 8 H2OII near 8 c (192 l). Structure factor calculations based on the space group Oh5 ‐ F m 3 m lead to the following final values of the reliability index R: 0.038 (Co3[Co(CN)6]2, 12 H2O) and 0.037 (Cd3[Co(CN)6]2, 12 H2O). The interatomic distances for the cobaltous compound (in parentheses for the cadmium compound) are: Co3+‐C: 1.88 Å (1.89); C‐N: 1.15 Å (1.17); Co2+‐N: 2.08 Å (2.24); Co2+‐OI: 2.10 Å (2.27); shortest OI‐H‐OII‐bonds: 2.89 Å (2.82). Co3+ is octahedrally coordinated by six carbon atoms, the divalent metal ion by four nitrogen atoms and two water molecules. The two different metal ions are connected by M2+‐N‐C‐Co3‐bonds to 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 Å.