Synthesis and crystal structure of bis(benzimidazolium) tetrahalocobaltate (II)

Abstract

The crystal structures of benzimidazolium tetrahalocobaltates (HBz)₂[CoX₄] (X = Cl and Br) have been determined. The chloride salt is triclinic, P-1, with a = 7.670(3) Å, b = 8.307(3) Å, c = 15.730(2) Å and α = 87.37(3)°, β = 84.99(3)°, γ = 67.72(2)°. The bromide salt is monoclinic, C2/c, with a = 15.568(2) Å, b = 8.063(3) Å, c = 5.762(2) Å and β = 91.36(3)°. The structures of the two salts are closely related. Both the compounds contain isolated tetrahedral CoX₄²⁻ anions and benzimidazolium cations. In the chloride salt, three chloride ions are involved in strong hydrogen bonding while only two bromide ions participate in the bromide salt. The greater deviation from the ideal tetrahedral geometry in CoBr₄²⁻ can be related to the less extensive hydrogen-bonding network compared to the chloro complex.