Two isomers Ba5Mg4C54O48H114 and Pb5Mg4C54O48H114

Abstract

There are reported two related structures of Ba₅Mg₄C₅₄O₄₈H₁₁₄ (dodeca(aqua-6κ ³O,7κ ³O,8κ ³O,9κ ³O)-tris(μ₂-propanoato-1:6κ ²O,1κO′)-tris(μ-propanoato-2:7κ ²O,2κO′-tris(μ-propanoato-3:8κ ²O,3κO′)-tris(μ-propanoato-4:9κ ²O,4κO′)-hexakis(μ₃-propanoato-1:5κ ²O,2:5κ ²O′;1:5κ ²O,3:5κ ²O′;1:5κ ²O,4:5κ ²O′;2:5κ ²O,3:5κ ²O′;2:5κ ²O,4:5κ ²O′;3:5κ ²O,4:5κ ²O′)-pentabarium tetramagnesium), (I), and Pb₅Mg₄C₅₄O₄₈H₁₁₄ (dodeca(aqua-1κ ³O,2κ ³O,3κ ³O,4κ ³O)-hexakis(μ₃-propanoato-1:5κ ²O,2:5κ ²O′;1:5κ ²O,3:5κ ²O′;1:5 κ ²O,4:5κ ²O′;2:5κ ²O,3:5κ ²O′;2:5κ ²O,4:5κ ²O′;3:5κ ²O,4:5κ ²O′)tetramagnesium lead(II) tris(propanoato-κ ²O,O′)plumbate(II)), (II). The title structures are compositional isomers which crystallize in the same space group type. The structure of (I) comprises molecules with symmetry 4 ‾ 3 m . The structure (II) comprises the complex cation {Pb(C₃H₅O₂)₆[Mg(H₂O)₃]₄}⁴⁺ with the symmetry 4 ‾ 3 m and four anions [tris(propanoato-κ ²O,O′)plumbate(II)]⁻, [Pb(C₃H₅O₂)₃]⁻ , with 3m symmetry. The central cations Ba1²⁺ and Pb1²⁺ in (I) and in the cation {Pb(C₃H₅O₂)₆[Mg(H₂O)₃]₄}⁴⁺ of the structure (II), respectively, have similar structural features which are comparable to the environment of the Ba²⁺ cation in BaCa₂(C₃H₅O₂)₆ [Stadnicka, K. & Glazer, A. M. (1980). Acta Cryst. B36, 2977–2985]. The molecules in (I) and the ions in (II) are interconnected by O_water‒H⋯O_propanoate hydrogen bonds of a moderate strength. The ethyl chains are disordered which is common in propanoates. However, there are unprecedented features in the title structures: 1) The central atom Pb1²⁺ is the first known example of a Pb²⁺ cation which is surrounded by six carboxylates in a bidentate bridging mode, i.e. by 12 oxygens. 2) The anion [tris(propanoato-κ ²O,O′)plumbate(II)]⁻ has a constitution with unusually prominent stereochemical activity of the 6s ² electron pair of the cation Pb²⁺ completing the coordination to the tetrahedral one. Thus, its formula can be expressed as [Pb^[ψ−4t](C₃H₅O₂)₃]⁻. 3) In both title structures, there are propanoate molecules with disordered carboxylate oxygens.