Nickel(II) perchlorate is a collection of inorganic compounds with the chemical formula of Ni(ClO4)2(H2O)x. Its colors of these solids vary with the degree of hydration. For example, the hydrate forms cyan crystals, the pentahydrate forms green crystals, but the hexahydrate (Ni(ClO4)2·6H2O) forms blue crystals. Nickel(II) perchlorate hexahydrate is highly soluble in water and soluble in some polar organic solvents.
Preparation Aqueous solutions of nickel(II) perchlorate can be obtained by treating nickel(II) hydroxide, nickel(II) chloride or nickel(II) carbonate with perchloric acid.
Ni(OH)2 + 2HClO4 + 4H2O → Ni(ClO4)2·6H2O Two hydrates have been characterized by X-ray crystallography: the hexahydrate and the octahydrate. Several other hydrates are mentioned including the pentahydrate, which is claimed to crystallize at room temperature, the nonahydrate, which is claimed to crystallize at −21.3 °C, a tetrahydrate, and a monohydrate. The yellow anhydrous product is obtained by treating nickel(II) chloride with chlorine trioxide. As deduced by X-ray crystallography, Ni resides in a distorted octahedral environment and the perchlorate ligands bridge between the Ni(II) centers.
Applications Nickel(II) perchlorates has few practical uses.
Other compounds Ni(ClO4)2 also forms some compounds with NH3, such as Ni(ClO4)2·6NH3 which is a light purple crystal. Ni(ClO4)2 also forms some compounds with N2H4, including Ni(ClO4)2·2N2H4 as a light positive solid or Ni(ClO4)2·5N2H4 which are purple crystals. Ni(ClO4)2 forms compounds with CO(NH2)2, like Ni(ClO4)2·6CO(NH2)2 which is a yellow-green solid. Ni(ClO4)2 forms compounds with CON3H5, for example Ni(ClO4)2·3CON3H5 which is a blue solid. Ni(ClO4)2 forms compounds with CON4H6, such as Ni(ClO4)2·3CON4H6 which is an explosive blue crystal with a bulk density of 0.95 g/cm3. Ni(ClO4)2 can also form compounds with CS(NH2)2, such as Ni(ClO4)2·6CS(NH2)2 which is a pale green solid. Ni(ClO4)2 also forms some compounds with CSN3H5, such as Ni(ClO4)2·2CSN3H5·3H2O which is a blue paramagnetic crystal or Ni(ClO4)2·3CSN3H5·2H2O which is a dark positive crystal. Ni(ClO4)2 also forms some compounds with pyridine.
Further reading D. Nicholls (2013), The Chemistry of Iron, Cobalt and Nickel Comprehensive Inorganic Chemistry, Elsevier, p. 1131, ISBN 978-1-4831-4643-0
See also Nickel Perchloric acid
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