Crystallographic investigations of diaquatetrachloro-cobalt(II) and nickel(II) complexes

The crystal structures of 2RbCl . CoCl2 . 2H(2)O (1) and 2RbCl . NiCl2 . 2H(2)O (2) have been determined by X-ray diffraction analyses. Both crystallize in triclinic space group <P(1)over bar> with a = 5.596(3), b = 6.486(3), c = 7.009(3) Angstrom, alpha = 65.35(2), beta = 87.68(2), gamma = 84.58(3)degrees, Z = 1 for 1, and a = 5.571(2), b = 6.450(3), c = 6.968(2) Angstrom, alpha = 65.52(4), beta = 87.57(3), gamma = 84.22(3)degrees, Z = 1 for 2. The Co2+ and 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)Cl-4(OH2)(2)](2-) (M(II) = Co, Ni) moieties are 2.479 and 2.437 Angstrom for 1 and 2, respectively, and the M(II)-O bond lengths are 2.017 and 2.070 Angstrom 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)Cl-2(OH2)(4)] octahedral moieties reported previously in M(II)Cl-2 . 4H(2)O and M(II)Cl-2 . 6H(2)O crystals.