Potassium trichloridocuprate(II) is a salt with chemical formula , more properly . It is a member of the "halide" sub-family of perovskite materials with general formula where is a monovalent cation, is a divalent cation, and is a

halide In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...

anion. The compound occurs in nature as the bright red mineral

sanguite Sanguite is a halide mineral. It is named after the Latin word ''sanguis'', meaning blood, due to its bright red colouration. It was approved as a valid species by the International Mineralogical Association in 2013. Characteristics Sanguite ...

. 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) .

Preparation and properties

The compound can be obtained by evaporation of a solution of

potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...

and copper(II) chloride in 1:1 mole ratio. The anhydrous form is garnet-red. It can be crystallized from a molten mixture of potassium chloride and copper(II) chloride . or by evaporation from a solution of the salts in ethanol. It is very hygroscopic, and soluble in

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

and ethanol. 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.

Structure

Anhydrous

The anhydrous mineral form (sanguite) has the monoclinic crystal structure, with

symmetry group In group theory, the symmetry group of a geometric object is the group of all transformations under which the object is invariant, endowed with the group operation of composition. Such a transformation is an invertible mapping of the ambient ...

''P''2₁/c and

lattice parameters Lattice may refer to: Arts and design * Latticework, an ornamental criss-crossed framework, an arrangement of crossing laths or other thin strips of material * Lattice (music), an organized grid model of pitch ratios * Lattice (pastry), an orna ...

''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. The measured density is 2.86 g/ cm³, close to the calculated one 2.88 g/cm³. It contains discrete almost planar anions , each with the two copper atoms connected by two bridging chlorine atoms. These anions are arranged in columns consisting of distorted edge-sharing octahedra, stacked in double chains parallel to the ''a'' axis. The columns occupy the edges and the centre of the cell's projection on the ''bc'' plane. The potassium atoms are located between these columns; each cation is surrounded by nine chlorine atoms. The mineral is optically biaxial (negative), with ''α'' = 1.653, ''β'' = 1.780, ''γ'' = 1.900', 2''V''= 85°. The mineral is named from the Latin ''sanguis'' (blood), alluding to its color. 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.

Theoretical

An alternative theoretical structure for the compound has a

cubic crystal system In crystallography, the cubic (or isometric) crystal system is a crystal system where the Crystal_structure#Unit_cell, unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There ...

, symmetry group ''P''m3m 21 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.

References

Potassium trichlorocuprate(1-)
. Chemical page 44145367 at the ''PubChem'' website. Accessed on 2022-07-18. {{cite journal , doi=10.3749/canmin.1500012 , title=Sanguite, KCuCl₃, A New Mineral from the Tolbachik Volcano, Kamchatka, Russia , year=2015 , last1=Pekov , first1=Igor V. , last2=Zubkova , first2=Natalia V. , last3=Belakovskiy , first3=Dmitry I. , last4=Lykova , first4=Inna S. , last5=Yapaskurt , first5=Vasiliy O. , last6=Vigasina , first6=Marina F. , last7=Sidorov , first7=Evgeny G. , last8=Pushcharovsky , first8=Dmitry Yu. , journal=The Canadian Mineralogist , volume=53 , issue=4 , pages=633–641 Chloro complexes Copper(II) compounds Potassium compounds