Metal-phenoxyalkanoic acid interactions. Part I. Crystal and molecular structures of diaquabis(p-chlorophenoxyacetato)zinc(II)

The crystal structures of diquabis(p-chlorophenoxyacetato)copper(II) (1) and diaquabis(phenoxyacetato)zinc(II) (2) have been determined by X-ray methods from diffractometer data and refined by least squares to R 03059 (1) and 03032 (2) for 999 and 1472 `observed' reflections respectively. Crystals of (1) are triclinic, space group P1 with Z = 1 in a unit cell of dimensions a = 7.065(3), b = 13.273(11), c = 5.114(2) Å, α = 93.72(5), β = 103.64(4), γ = 81.63(5)°. The complex has a centrosymmetric tetragonally-distorted octahedral stereochemistry, the coordination sphere consisting of two water oxygens [CuO, 1.960(4) Å] and two carbonyl oxygens [CuO, 1.956(4) Å] from different bidentate phenoxyacetate ligands about the square plane while the axial positions are occupied by two ether oxygens [CuO, 2.406(4) Å]. The water oxygens are tied into a two-dimensional hydrogen-bonded network involving the un-co-ordinated carboxyl oxygens (O⋯O, 2.652 Å) and the co-ordinated carboxyl oxygens with the O(H)⋯O distances of 2.164 and 2.708 Å respectively. Compound (2) is monoclinic, spacegroup C2 with Z = 2 in a cell of dimensions a = 11.625(3), b = 5.221(1), c = 13.767(4) Å, β = 101.05(5)°. The complex (2) possesses a distorted trapezoidal pyramidal stereochemistry involving two water oxygens [ZnO, 1.994(1) Å] and four carboxyl oxygens from phenoxyacetate ligands [ZnO, 2.118(1) Å]. In both structures the phenoxy ligands are essentially planar and have similar distances and angles to those found in the structure fo un-co-rdinated phenoxyacetic acid. Single-crystal and powder diffractionaer X-ray data are also reported for diaquabis(p-chlorphenoxyacetato)zinc(II) (3), which is isostructural with (2)

Metal-phenoxyalkanoic acid interactions. Part 6. Crystal and molecular structure of tetraaquabis(2,4-dichlorophenoxyacetato) zinc(II)diaquabis(2,4-dichlorophenoxyacetato)zinc(II)

The crystal structure of tetraquabis(2,4-dichlorophenoxyacetato)zinc(II) diaquabis(2,4-dichlorophenoxyacetato)zinc(II) has been determined by direct methods from three-dimensional X-ray diffraction data and refined by least squares to a residual value of 0.068 for 2703 'observed' reflections. Crystals are orthorhombic, space group Pna2 with 4 molecular 'dimers' in a cell of dimensions a = 19.302(2), b = 6.051, c = 36.325(6) Å. The molecular units, {[Zn(HO)(2,4-D)][Zn(HO)(2,4-D)]} consist of two discrete and stereochemically different complexes, one octahedral, the other tetrahedral about the zinc centres. The six-coordination about the first Zn comprises four oxygens from aqua ligands [ZnO, 2.069(10)-2.147(9) rA] and two from the carboxyl groups of trans-related unidentate 2,4-dichlorophenoxyacetato ligands [ZnO, 2.071(9), 2.121(9) Å]. The un-complexed carboxylate oxygens are tied into the complex unit by intramolecular hydrogen bonds to the water ligands (O⋯O, 2.66, 2.64 Å). The four-coordination about the second Zn comprises two aqua ligands [ZnO, 2.003(10), 2.001(9) Å] and two unidentate carboxyl oxygens from 2,4-dichlorophenoxyacetato ligands [ZnO, 1.915(10), 1.956(9) Å]. The two units are not formally bonded but have inter-molecular O⋯O associations ranging from 2.68 to 2.85 Å