Abstract
There are reported two related structures of Ba 5 Mg 4 C 54 O 48 H 114 (dodeca(aqua-6 κ 3 O,7 κ 3 O,8 κ 3 O,9 κ 3 O)-tris(μ 2 -propanoato-1:6 κ 2 O,1 κ O′)-tris(μ-propanoato-2:7 κ 2 O,2 κ O′-tris(μ-propanoato-3:8 κ 2 O,3 κ O′)-tris(μ-propanoato-4:9 κ 2 O,4 κ O′)-hexakis(μ 3 -propanoato-1:5 κ 2 O,2:5 κ 2 O′;1:5 κ 2 O,3:5 κ 2 O′;1:5 κ 2 O,4:5 κ 2 O′;2:5 κ 2 O,3:5 κ 2 O′;2:5 κ 2 O,4:5 κ 2 O′;3:5 κ 2 O,4:5 κ 2 O′)-pentabarium tetramagnesium), (I), and Pb 5 Mg 4 C 54 O 48 H 114 (dodeca(aqua-1 κ 3 O,2 κ 3 O,3 κ 3 O,4 κ 3 O)-hexakis(μ 3 -propanoato-1:5 κ 2 O,2:5 κ 2 O′;1:5 κ 2 O,3:5 κ 2 O′;1:5 κ 2 O,4:5 κ 2 O′;2:5 κ 2 O,3:5 κ 2 O′;2:5 κ 2 O,4:5 κ 2 O′;3:5 κ 2 O,4:5 κ 2 O′)tetramagnesium lead(II) tris(propanoato- κ 2 O,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 $\overline{4}3m$ . The structure (II) comprises the complex cation {Pb(C 3 H 5 O 2 ) 6 [Mg(H 2 O) 3 ] 4 } 4+ with the symmetry 4 ‾ 3 m $\overline{4}3m$ and four anions [tris(propanoato- κ 2 O,O′)plumbate(II)] − , [Pb(C 3 H 5 O 2 ) 3 ] − , with 3 m symmetry. The central cations Ba1 2+ and Pb1 2+ in (I) and in the cation {Pb(C 3 H 5 O 2 ) 6 [Mg(H 2 O) 3 ] 4 } 4+ of the structure (II), respectively, have similar structural features which are comparable to the environment of the Ba 2+ cation in BaCa 2 (C 3 H 5 O 2 ) 6 [Stadnicka, K. & Glazer, A. M. (1980). Acta Cryst . B 36 , 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 Pb1 2+ is the first known example of a Pb 2+ cation which is surrounded by six carboxylates in a bidentate bridging mode, i.e. by 12 oxygens. 2) The anion [tris(propanoato- κ 2 O,O′)plumbate(II)] − has a constitution with unusually prominent stereochemical activity of the 6 s 2 electron pair of the cation Pb 2+ completing the coordination to the tetrahedral one. Thus, its formula can be expressed as [Pb [ ψ −4 t ] (C 3 H 5 O 2 ) 3 ] − . 3) In both title structures, there are propanoate molecules with disordered carboxylate oxygens.
