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

The structures of the sodium, potassium and rubidium complex salts of (4‐fluorophenoxy)acetic acid (PFPA), namely polyμ‐aqua‐aqua‐μ‐2‐(4‐fluorophenoxy)acetato]‐κ³O ¹,O ²:O^1′‐sodium], Na(C₈H₆FO₃)(H₂O)₂]_n , (I), and isotypic polyμ₅‐2‐(4‐fluorophenoxy)acetato]‐κ⁵O ¹,O ²:O ¹,O ^1′:O ^1′:O ^1′:O^1′‐potassium], K(C₈H₆FO₃)]_n , (II), and polyμ₅‐2‐(4‐fluorophenoxy)acetato]‐κ⁵O ¹,O ²:O ¹,O ^1′:O ^1′:O ^1′:O^1′‐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 M O₇ 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.