Hydro­thermal synthesis and crystal structure of a new lanthanum(III) coordination polymer with fumaric acid

The title compound, poly[di­aqua­tris­(μ4-but-2-enedioato)(μ2-but-2-enedioic acid)dilanthanum(III)], [La2(C4H2O4)3(C4H4O4)(H2O)2]n, was synthesized by the reaction of lanthanum chloride penta­hydrate with fumaric acid under hydro­thermal conditions. The asymmetric unit comprises an LaIII cation, one and a half fumarate dianions (L2−), one a half-mol­ecule of fumaric acid (H2L) and one coordinated water mol­ecule. Each LaIII cation has the same nine-coordinate environment and is surrounded by eight O atoms from seven distinct fumarate moieties, including one proton­ated fumarate unit and one water mol­ecule in a distorted tricapped trigonal–prismatic environment. The LaO8(H2O) polyhedra centres are edge-shared through three carboxyl­ate bridges of the fumarate ligand, forming chains in three dimensions to construct the MOF. The crystal structure is stabilized by O—H⋯O hydrogen-bond inter­actions between the coordin­ated water mol­ecule and the carboxyl­ate O atoms, and also between oxygen atoms of fumaric acid