Synthesis,structural, and spectroscopic characterization of hexakis (dimethyl sulfoxide)cobalt(II) tetrachlorocobaltate(II), [Co(Me2SO)6][CoCl4]

Well-formed single crystals of a compound having the empirical formula CoCl₂·3Me₂SO have been prepared using a vapour diffusion technique. X-ray diffraction methods confirm the previous spectrophotometric results of Cotton and Francis (1960a) and unequivocally demonstrate that this compound must be formulated as [Co(Me₂SO)₆]²⁺[CoCl₄]^2–. The compound crystallizes in the triclinic space groupP¯1 witha=18.601(3),b=9.613(2),c=9.044(2),=87.50(2)°,=98.64(2)°, =98.44(2)° andZ=2. Although a significant decrease of crystal quality with time and severe molecular disorder of Me₂SO are present, we have determined the coordination geometry around the cobalt centers. One cobalt atom is bound to six oxygen atoms of the Me₂SO moiety in a slightly distorted octahedral configuration; the mean Co-O distance is 2.083(12)Å. The second cobalt atom is surrounded by four chloride anions in an approximately tetrahedral configuration; the mean Co-Cl distance is 2.284(6) Å. The structure of the complex has been also investigated by means of ir measurements in the 4000-200 cm^–1 range.