Synthesis and Crystal Structure of the [Co(en)3][Co(NO2)6]·3H2O Double Complex Salt

Crystals of the [Co(en)3][Co(NO2)6]·3H2O (1) double complex salt (DCS) are prepared upon isothermal evaporation of an aqueous solution containing [Co(en)3]Cl3 and Na3[Co(NO2)6] in the 1:1 molar ratio. The new compound is trigonal, space group R32, a = 12.9915(4) Å, c = 11.7113(4) Å, V = 1711.81(9) Å3. Its crystal structure is characterized by partial disorder due to the incompatibility local symmetry of the [Co(NO2)6]3– anion and the overall symmetry of the structure. In contrast to most DCSs containing structurally similar [Co(NH3)6]3+ cation, the hydrate 1 is well soluble in water.