Two-dimensional coordination polymeric structures in the sodium, potassium and rubidium complex salts with (4-fluorophenoxy)acetic acid.

Abstract

The structures of the sodium, potassium and rubidium complex salts of (4-fluorophenoxy)acetic acid (PFPA), namely poly[μ-aqua-aqua-μ-[2-(4-fluorophenoxy)acetato]-κ3O1,O2:O1'-sodium], [Na(C8H6FO3)(H2O)2]n, (I), and isotypic poly[μ5-[2-(4-fluorophenoxy)acetato]-κ5O1,O2:O1,O1':O1':O1':O1'-potassium], [K(C8H6FO3)]n, (II), and poly[μ5-[2-(4-fluorophenoxy)acetato]-κ5O1,O2:O1,O1':O1':O1':O1'-rubidium], [Rb(C8H6FO3)]n, (III), have been determined and their coordination polymeric structures described. In the structure of (I), the very distorted octahedral NaO6 coordination polyhedron comprises two bidentate chelating O-atom donors (carboxylate and phenoxy) of the PFPA ligand and three O-atom donors from water molecules, one monodentate and the other μ2-bridging between inversion-related Na centres in a cyclic manner. A bridging carboxylate donor generates two-dimensional polymer layers lying parallel to (001), in which intralayer water O-H...O hydrogen-bonding associations are also present. Structures (II) and (III) are isotypic, each having an irregular MO7 stereochemistry, with the primary metal-ligand bidentate chelate similar to that in (I) and extended into a two-dimensional polymeric layered structure, lying parallel to (100), through five additional bridging carboxylate O atoms. Two of these bonds are from an O,O'-bidentate chelate interaction and the other three are from μ3-O-atom bridges, generating cyclic links with short M...M separations [3.9064 (17) Å for (II) and 4.1001 (8) for (III)], the shortest being a centrosymmetric four-membered cyclic link. In the crystals of (I)-(III), intralayer C-H...F interactions are present, but no π-π ring interactions are found.