Potassium trichloridocuprate(II) is a salt with chemical formula KCuCl3, more properly [K+]2[Cu2Cl2−6].[3][4]
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| KCuCl3 | |
| Molar mass | 208.99 g·mol−1 |
| Appearance | garnet-red crystals[1] |
| Density | 2.86 g/cm3[1] |
| Solubility | methanol,[2] ethanol[2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
It is a member of the "halide" sub-family of perovskite materials with general formula ABX3 where A is a monovalent cation, B is a divalent cation, and X is a halide anion.[5]
The compound occurs in nature as the bright red mineral sanguite.[1]
The compound is also called potassium trichlorocuprate(II), potassium copper(II) trichloride, potassium cupric chloride and other similar names. The latter is used also for potassium tetrachloridocuprate(II) K2CuCl4.[1]
Preparation and properties
The compound can be obtained by evaporation of a solution of potassium chloride KCl and copper(II) chloride CuCl2 in 1:1 mole ratio.[3]
The anhydrous form is garnet-red.[6] It can be crystallized from a molten mixture of potassium chloride KCl and copper(II) chloride CuCl2.[7][2] or by evaporation from a solution of the salts in ethanol.[5] It is very hygroscopic,[5] and soluble in methanol and ethanol.[2] It is antiferromagnetic below 30 K, and pleochroic, with maximum visible absorption when the electric vector is parallel to the Cu–Cu vector of the dimer.[6][8]
Structure
Anhydrous
The anhydrous mineral form (sanguite) has the monoclinic crystal structure, with symmetry group P21/c and lattice parameters a = 402.81 pm, b = 1379.06 pm, c = 873.35 pm, and β = 97.137°, cell volume V = 0.48138 nm3, and formulas per cell Z = 4.[1][9] The measured density is 2.86 g/cm3, close to the calculated one 2.88 g/cm3. It contains discrete almost planar anions [Cu2Cl6]2−, each with the two copper atoms connected by two bridging chlorine atoms. These anions are arranged in columns consisting of distorted edge-sharing CuCl6 octahedra, stacked in double chains parallel to the a axis. The columnsoccupy the edges and the centre of the cell's projection on the bc plane.[1][9][6] The potassium atoms are located between these columns; each K+ cation is surrounded by nine chlorine atoms.[1] The mineral is optically biaxial (negative), with α = 1.653, β = 1.780, γ = 1.900', 2V= 85°. The mineral is named from the Latin sanguis (blood), alluding to its color.[1]
Theoretical calculations for this topology give the lattice parameters as a = 1388.1 pm, b = 427.7 pm, c = 896.5 pm, α = 79.855°, cell volume V = 0.523891 nm3, calculated density 2.65 g/cm3.[10]
Theoretical
An alternative theoretical structure for the compound has a cubic crystal system, symmetry group Pm3m[221], with the copper atoms arranged as corners of a cubic grid, a potassium atom at the center of each cube and a chlorine atom at the midpoint of each edge. The latice parameters are a = b = c = 485.8 pm, V = 0.114684 nm3, predicted density 3.03 g/cm3.[11]