Metal-phenoxyalkanoic acid interactions. XXV the crystal structures of (2-Formyl-6-methoxyphenoxy)acetic acid and its zinc(II) complex and the lithium, zinc(II) and cadmium(II) complexes of (2-chlorophenoxy)acetic acid

The crystal structures of (2-formyl-6-methoxyphenoxy)acetic acid (1), diaquabis[(2-formyl-6-methoxyphenoxy)acetato]zinc(II) (2), tetraaquabis[(2-chlorophenoxy)acetato]zinc(II) (3), triaquabis[(2-chlorophenoxy)acetato]cadmium(II) dihydrate (4) and lithium (2-chloro-phenoxy)acetate 1·5 hydrate (5) have been determined by X-ray diffraction. The acid (1) forms centrosymmetric hydrogen-bonded cyclic dimers [O···O, 2·677(6) Å] which are non-planar. Complex (2) is six-coordinate with two waters [Zn-O, 1·997(2) Å] and four oxygens from two asymmetric bidentate carboxyl groups [Zn-O, 2·073, 2·381(2) Å] completing a skew trapezoidal bipyramidal stereochemistry. Complex (5) is also six-coordinate but is octahedral, with two trans-related unidentate carboxyl oxygens [mean Zn-O, 2·134(9) Å] and four waters [mean Zn-O, 2·081(9) Å], The seven-coordinate complex (4) has crystallographic twofold rotational symmetry relating two asymmetric bidentate acid ligands [Cd-O, 2·26, 2·48(2) Å] and two waters [Cd-O, 2·34(2) Å] while the third water lies on this axis [Cd-O, 2·27(2) Å], In contrast to the monomers (2)-(4), complex (5) is polymeric with tetrahedral lithium coordinated to one water and three carboxylate oxygens [mean Li-O, 1·95(1) Å], The essential conformation of the free acid is retained in complexes (2), (3) and (4) but in (5), it is considerably changed