Formation of [CoCl4(H2O)2]2− complex in CoCl2·MgCl2·8H2O double salt: structural and energetic properties of [MCl4(H2O)2]2− and [M(H2O)6]2+ (M=Mg, Co)
Review articleOpen access
2003/08/01 Full-length article DOI: 10.1016/S0022-4596(03)00210-X
Journal: Journal of Solid State Chemistry
AbstractThe crystal structure of the double salt CoCl2·MgCl2·8H2O has been determined by the X-ray diffraction method. It crystallizes in the space group P1̄ with a=6.0976(9), b=6.308(1), c=8.579(3) Å, α=81.99(2)°, β=88.40°, γ=84.61(1)°, Z=1, and R=0.027. The crystal consists of two kinds of well separated octahedra, [CoCl4(H2O)2]2− and [Mg(H2O)6]2+. The former is unique as aquachloro complexes of Co2+. In order to elucidate the reason prepared as such unique complexes in the double salts, formation energies for [MCl4(H2O)2]2− and [M(H2O)6]2+ (M=Co, Mg) have been calculated by using the density functional methods, and it has been revealed that the formation energies of the first coordination sphere for the metal ions and the Cl−⋯H2O hydrogen bond networks around [CoCl4(H2O)2]2− play a decisive role in forming [CoCl4(H2O)2]2− with the regular octahedral geometry in the double salt.
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