The structure of the title compound, catena-poly[[[di-μ-aqua-μ-fumarato-μ-(boric acid)-disodium]-di-μ-aqua] boric acid monosolvate], contains two crystallographically independent Na+ cations, each being six-coordinated by one fumarate O atom, one boric acid O atom and four water O atoms in a distorted octahedral geometry. Adjacent [NaO2(OH2)4] units share edges and are linked into chains propagating parallel to [100]. The free boric acid molecules are connected to the chains through strong intermolecular O—H
O hydrogen bonds. Additional O—HO hydrogen bonds between the water molecules, the free and coordinated boric acid molecules and the fumarate anion lead to the formation of a three-dimensional supramolecular structure. With the exception of the two water molecules, all other atoms lie on mirror planes.
O hydrogen bonds. Additional O—HO hydrogen bonds between the water molecules, the free and coordinated boric acid molecules and the fumarate anion lead to the formation of a three-dimensional supramolecular structure. With the exception of the two water molecules, all other atoms lie on mirror planes.