Potassium tetrachloridocuprate(II) describes salts with chemical formula K2CuCl4(H2O)2. It is a greenish blue solid. This form also occurs naturally as the rare mineral mitscherlichite.
Synthesis and natural occurrence The dihydrate occurs rarely in nature near volcanic vents, e.g. in Mount Vesuvius, as the mineral mitscherlichite; which is named in honor of Eilhardt Mitscherlich (1794–1863), the German crystallographer and chemist who first synthesized the compound. It was identified as pigment in some ancient artifacts. The dihydrate can be obtained by slow evaporation of a solution of potassium chloride () and copper(II) chloride () in 2:1 molar ratio.
Structure
The structure of hydrated potassium tetrachloridocuprate(II) has been confirmed by X-ray crystallography and neutron diffraction. Copper is square planar, being bound to two trans chloride ligands (dCu-Cl = 228 pm and two water ligands (dCu-O = 1.97 pm). The other chlorides are more distant (Cu-Cl = 289 pm). Structural studies on this salt are of historic interest. The compound is isostructural with and .
Tetrachlorocuprates Anhydrous has a complicated history and may not exist. Instead it converts upon heating to a mixture of and potassium trichloridocuprate .
The ion has been intensively studied from the perspective of electronic structure. It is a planar complex, usually isolated as a salt with organic cations.
See also
Potassium trichloridocuprate(II),
References Sterling B. Hendricks and Roscoe G. Dickinson (1927). The crystal structures of ammonium, potassium and rubidium cupric chloride dihydrates. Journal of the American Chemical Society, volume 49, issue 9, pages 2149–2162 L. Chrobak (1934). Quantitative spectrometric studies of ammonium and of potassium cupric chloride dihydrate (NH4)2CuCl4.2H2O and K2CuCl4.2H2O. Zeitschrift für Kristallographie, volume 88, pages 35–47 C. M. Fontana, E. Gorin, G. A. Kidder and C. S. Meredith (1952). Ind. Eng. Chem., volume 44, page 363 S. A. Shchukarev, I. V. Vasil'kova and G. M. Barvinok (1965). Vestn. Leningr. Univ., Ser. Mat. Fiz. Khim., volume 20, page 145.
I. V. Vasil'kova and G. M. Barvinok (1966). Chemical Abstracts, volume 65, page 9831.
E. Joly (1971). C. R. Acad. Sci., Ser. C, volume 271, page 1302. Howard E. Swanson, Howard F. McMurdie, Marlene C. Morris, Eloise H. Evans, and Boris Paretzkin (1971) Potassium Copper Chloride Hydrate (mitscherlichite), in [Standard X-ray Diffraction Powder Patterns] National Bureau of Standards, Monograph 25, Section 9; page 34. H. T. Witteveen, D. L. Jongejan and W. Brandwijk (1974). Mater. Res. Bull., volume 9, page 345. N. Fogel and T. J. Nolan (1975). Amer. Chem. Soc. Symp., section Inorg., page 121. D. W. Smith (1976), Chlorocuprates(II). Coordination Chemistry Reviews, volume 21, issues 2-3, pages 93-158. Thomas J. Nolan, Harold Haralson, James L. McAdams and Norman Fogel (1977) Dehydration of potassium tetrachlorocuprate(II) dihydrate. Journal of the Chemical Society, Dalton Transactions, volume 1977, issue 17, pages 1608-1612 Riederer (1982) John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, and Monte C. Nichols (1997) Mitscherlichite, in Handbook of Mineralogy, Mineralogical Society of America. volume III.