Polymeric tetraaquatris(malonato)dilanthanum(III) monohydrate

Abstract

The title compound, [La2(C3H2O4)3(H2O)4]·H2O, forms a layer‐type polymeric structure. The layers, which contain infinite puckered four‐membered La—O—La—O rings in a pseudo‐ternary symmetry, are formed by the lanthanum and one independent malonate group. They are interconnected by the second independent malonate group, giving a three‐dimensional framework in which wide channels accommodate one disordered water mol­ecule of crystallization. The La atom lies on a twofold axis and is ten‐coordinated by eight O atoms from carboxyl­ate groups and two water mol­ecules. One malonate group is monodentate and triply bridging chelating, whilst the other is doubly monodentate. The extensive network of hydrogen bonds and bridge bonds observed in this structure enhances the structural stability. Despite some identical subfeatures, this structure is quite different from that observed in [La2(C3H2O4)3(H2O)3]·2H2O.

Poly[[tetraaquatris(μ3-2,2-dimethylmalonato)dilanthanum(III)] monohydrate]

“…The La-O distances in (I) ( Table 1) are comparable with the values reported for polymeric tetraaquatrimalonatodilanthanum(III) monohydrate (Benmerad et al, 2000), but with three La-O bonds being considerably longer. These longer distances seem to be rather typical of the chelating carboxyl-…”

“…A comparison with the two previously reported lanthanum malonate compounds (Marrot & Trombe, 1993;Benmerad et al, 2000) reveals that all these structures contain the same number of water molecules. However, the two crystallographically independent La atoms of the former are nineand eight-coordinate, respectively, while in the latter there is only one crystallographically independent La atom and two independent malonate dianions.…”

“…The L3 ligand also adopts two bis-bidentate 1,2-chelating modes and one sixmembered chelating mode to connect to atoms La2, La1 ii and La2 ii , but it differs from the L2 ligand with the bond angle at C12 being smaller than the normal value (Table 1), indicating that there is greater distortion in this six-membered ring. This smaller angle was observed in polymeric tetraaquatrimalonatodilanthanum(III) monohydrate complexes (Benmerad et al, 2000).…”

“…The La geometries do not approximate to an idealized polyhedron, a bicapped square antiprism or a bicapped dodecahedron. This is not surprising in view of the steric requirements of the dimethylmalonate ligands in the structure and the large distortions imposed by the bite angles, which are considerably small (Table 1) (see Benmerad et al, 2000). Through the centres of inversion, each group of six La2 atoms and four La1 atoms builds up a decanuclear 20-membered ring.…”

catena-Poly[[aquabarium(II)]-μ-aqua-bis(μ-2′-carboxybiphenyl-2-carboxylato)]

“…The increasing interest is principally due to the tunability of the resulting extended frameworks. Among the previously studied compounds are several layered compounds (Wan et al, 2002;Benmerad, Guehria-Laõ Èdoudi, Bernardinelli & Balegroune, 2000), singlestrand polymers (Tu et al, 2005;Benmerad, Guehria-Laidoudi, Balegroune et al, 2000;Benmerad et al, 2004b) and three-dimensional crosslinked polynuclear units (Pan et al, 2001;Benmerad et al, 2004a;Djeghri et al, 2006). These compounds typically exhibit in®nite MÐOÐM chains and several poly-membered rings, which favour interactions between the metal atoms and create various kinds of voids.…”