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

Abstract

The crystal structures of (2-formyl-6-methoxyphenoxy)acetic acid (1), diaquabis [(2-formyl-6-methoxyphenoxy) acetato ]zinc(11) (2), tetraaquabis [(2-chlorophenoxy) acetato ]zinc(11) (3), triaquabis [(2-chlorophenoxy) acetato ]cadmium(11) 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…0, 2.677(6) Å] which are non-planar. Complex (2) is six-coordinate with two waters [Zn- O_w , 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 :symmetric bidentate acid ligands [ Cd -O, 2.26, 2 48(:) 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-0, 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.