Stereochemical activity of a lone electron pair in antimony(III) and bismuth(III) chelates: Crystal structures of Ca[Sb(Edta)]2 ⋅ 8H2O and Ba{[Bi(Edta)] 2H2O ⋅ H2O

Abstract

The crystal structures of Ca[Sb(Edta)]2 ⋅ 8H2O (I) and Ba{ [Bi(Edta)]2H2O} ⋅ H2O (II) are determined by X-ray diffraction. Crystals I are monoclinic, a = 7.132 A, b = 21.906 A, c = 10.896 A, β = 91.13°, Z = 2, and space group P21/n. Crystals II are triclinic, a = 8.995 A, b = 12.750 A, c = 13.577 A, α = 77.42°, β = 73.90°, γ = 86.53°, Z = 2, and space group $$P\bar 1$$ . In structure I, the coordination number of the antimony atom is 6 + LEP (lone electron pair), and the polyhedron is a ψ-pentagonal bipyramid with the lone electron pair at an equatorial position. In structure II, two crystallographically independent complexes Bi(Edta)− and the coordination water molecule form tetranuclear associates. The environments of two independent bismuth atoms (the coordination number is eight) are similar, and their polyhedra can be described as distorted dodecahedra. The effect of the lone electron pair on the structures of polyhedra of antimony and bismuth is discussed.