Copper(II) carbonate

The stability of dry depends critically on the partial pressure of carbon dioxide ({{chem2|p_{CO2} }}). It is stable for months in dry air, but decomposes slowly into and if {{chem2|p_{CO2} }} is less than . In the presence of water or moist air at , is stable only for {{chem2|p_{CO2} }} above and pH between about 4 and 8. Below that partial pressure, it reacts with water to form a basic carbonate (azurite, ). : In highly basic solutions, the complex anion is formed instead. The solubility product of the true copper(II) carbonate was measured by Reiterer and others as pKso = 11.45 ± 0.10 at . ==Structure==

In the crystal structure of , copper adopts a distorted square pyramidal coordination environment with coordination number 5. Each carbonate ion bonds to 5 copper centres. File:Copper(II)-carbonate-unit-cell-3D-bs-N17-M25.png|Unit cell of CuCO3 File:Copper(II)-carbonate-xtal-Cu-coordination-3D-bs-N17-M25.png|Copper coordination environment File:Copper(II)-carbonate-xtal-carbonate-coordination-3D-bs-N17-M25.png|Carbonate coordination environment ==Preparation==

Reactions that may be expected to yield , such as mixing solutions of copper(II) sulfate and sodium carbonate in ambient conditions, yield instead a basic carbonate and , due to the great affinity of the ion for the hydroxide anion . Thermal decomposition of the basic carbonate at atmospheric pressure yields copper(II) oxide rather than the carbonate. In 1960, C. W. F. T. Pistorius claimed synthesis by heating basic copper carbonate at in an atmosphere of carbon dioxide at and water at for 36 hours. The bulk of the products was well-crystallized malachite , but a small yield of a rhombohedral substance was also obtained, claimed to be . However, this synthesis was apparently not reproduced. Reliable synthesis of true copper(II) carbonate was reported for the first time in 1973 by Hartmut Ehrhardt et al. The compound was obtained as a gray powder, by heating basic copper carbonate in an atmosphere of carbon dioxide (produced by the decomposition of silver oxalate,) at and . The compound was determined to have a monoclinic structure. ==References==