CRYSTALLOGRAPHIC INVESTIGATIONS OF DIAQUATETRACHLORO-COBALT(II) AND NICKEL(II) COMPLEXES

Abstract

The crystal structures of 2RbCl·CoCl₂·2H₂O (1) and 2RbCl·NiCl₂·2H₂O (2) have been determined by X-ray diffraction analyses. Both crystallize in triclinic space group P 1 with a = 5.596(3), b = 6.486(3), c = 7.009(3) Å, α = 65.35(2), β = 87.68(2), γ = 84.58(3)°, Z = 1 for 1, and a = 5.571(2), b = 6.450(3), c = 6.968(2) Å, α = 65.52(4), β = 87.57(3), γ = 84.22(3)°, Z = 1 for 2. The Co²⁺ and Ni²⁺ atoms are both coordinated in distorted trans-octahedral geometries by four Cl⁻ and two water molecules, and Rb⁺ is surrounding by eight Cl⁻ ions. The average interatomic distances between the first transition metal(II) and chloride ions in trans-[M(II)Cl₄(OH₂)₂]^2- (M(II) = Co, Ni) moieties are 2.479 and 2.437 Å for 1 and 2, respectively, and the M(II)-O bond lengths are 2.107 and 2.070 Å for 1 and 2, respectively. With the same M(II) cations, the M(II)-Cl distance is significantly longer than those of cis- and trans-[M(II)Cl₂(OH₂)₄] octahedral moieties reported previously in M(II)Cl₂ · 4H₂O and M(II)Cl₂ · 6H₂O crystals.

Key Words:

• X-ray structure
• double salt
• cobalt(II)
• nickel(II)
• chloride