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Cobalt(II) hydroxide
Cobalt(II) hydroxide or cobaltous hydroxide is the inorganic compound with the formula Co(OH)
2, consisting of divalent cobalt cations Co2+
and hydroxide anions OH−
. The pure compound, often called the "beta form" (β-Co(OH)
2) is a pink solid insoluble in water.
The name is also applied to a related compound, often called "alpha" or "blue" form (α-Co(OH)
2), which incorporates other anions in its molecular structure. This compound is blue and rather unstable.
Cobalt(II) hydroxide is most used as a drying agent for paints, varnishes, and inks, in the preparation of other cobalt compounds, as a catalyst and in the manufacture of battery electrodes.
Cobalt(II) hydroxide precipitates as a solid when an alkali metal hydroxide is added to an aqueous solution of Co2+ salt. For example,
The compound can be prepared by reacting cobalt(II) nitrate in water with a solution of triethylamine N(C
2H
5)
3 as both the base and a complexing agent. It can also be prepared by elecrolysis of a solution of cobalt nitrate with a platinum cathode.
Cobalt(II) hydroxide decomposes to cobalt(II) oxide at 168 °C under vacuum and is oxidized by air. The thermal decomposition product in air above 300 °C is Co3O4.
Like iron(II) hydroxide, cobalt(II) hydroxide is a basic hydroxide, and reacts with acids to form cobalt(II) salts. It also reacts with strong bases to form solutions with dark blue cobaltate(II) anions, [Co(OH)4]2− and [Co(OH)6]4−.
The (β) form of cobalt(II) hydroxide has the brucite crystal structure, i.e. the arrangement of the atoms in the crystal are the same as the arrangement of the atoms in Mg(OH)2. The Co(II) centers are bonded to six hydroxide ligands. Each hydroxide ligand bridges to three Co(II) sites. The O-H bonds are perpendicular to the planes defined by the oxygen atoms, projecting above and below these layers. Ignoring the H atoms, the packing of the anion and cations is also described as the cadmium iodide structure, in which the cobalt(II) cations have octahedral molecular geometry.
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Cobalt(II) hydroxide
Cobalt(II) hydroxide or cobaltous hydroxide is the inorganic compound with the formula Co(OH)
2, consisting of divalent cobalt cations Co2+
and hydroxide anions OH−
. The pure compound, often called the "beta form" (β-Co(OH)
2) is a pink solid insoluble in water.
The name is also applied to a related compound, often called "alpha" or "blue" form (α-Co(OH)
2), which incorporates other anions in its molecular structure. This compound is blue and rather unstable.
Cobalt(II) hydroxide is most used as a drying agent for paints, varnishes, and inks, in the preparation of other cobalt compounds, as a catalyst and in the manufacture of battery electrodes.
Cobalt(II) hydroxide precipitates as a solid when an alkali metal hydroxide is added to an aqueous solution of Co2+ salt. For example,
The compound can be prepared by reacting cobalt(II) nitrate in water with a solution of triethylamine N(C
2H
5)
3 as both the base and a complexing agent. It can also be prepared by elecrolysis of a solution of cobalt nitrate with a platinum cathode.
Cobalt(II) hydroxide decomposes to cobalt(II) oxide at 168 °C under vacuum and is oxidized by air. The thermal decomposition product in air above 300 °C is Co3O4.
Like iron(II) hydroxide, cobalt(II) hydroxide is a basic hydroxide, and reacts with acids to form cobalt(II) salts. It also reacts with strong bases to form solutions with dark blue cobaltate(II) anions, [Co(OH)4]2− and [Co(OH)6]4−.
The (β) form of cobalt(II) hydroxide has the brucite crystal structure, i.e. the arrangement of the atoms in the crystal are the same as the arrangement of the atoms in Mg(OH)2. The Co(II) centers are bonded to six hydroxide ligands. Each hydroxide ligand bridges to three Co(II) sites. The O-H bonds are perpendicular to the planes defined by the oxygen atoms, projecting above and below these layers. Ignoring the H atoms, the packing of the anion and cations is also described as the cadmium iodide structure, in which the cobalt(II) cations have octahedral molecular geometry.