POLYMERIC COMPLEXES OF 3-HYDROXY-4-METHOXY AND 3-METHOXY-4-HYDROXYBENZOIC ACIDS - CRYSTAL-STRUCTURE OF THE LINEAR-CHAIN COMPLEX OF CO(II) WITH 3-HYDROXY-4-METHOXYBENZOIC ACID

Reaction of Cu̎, Co̎, and Ni̎ with 3-hydroxy-4-methoxy- and 3-methoxy-4-hydroxybenzoic acids (hmba and mhba, respectively) yields hydrated complexes exhibiting stoicheiometries with 1:2 and 1:1 metal to ligand mol ratios. The 1:2 complexes, formed by Co̎ with hmba and Cu̎ with mhba, involve carboxylate groups and water molecules as donors. The structure of [Co(hmba)2(H2O)3] was determined by singlecrystal X-ray analysis. It crystallizes in the monoclinic space group I2/a with a = 8.164(2), b = 11.171(3), c = 20.980(5)Å, β = 91.42(3)°, and Z = 4. The complex is a one-dimensional polymer with bridging water molecules (Co-H2O-Co = 128.04° and Co … Co = 4.082 Å). The hexacoordination at each cobalt is completed by oxygens from two monodentate carboxylates and two water molecules. Stacking interactions between the parallel aromatic rings (3.5 Å) hold neighbouring chains together. Complexes aith a I:1 metal to ligand ratio (M = Cu̎, Co̎ and Ni̎, L = hmba; M = Co̎ and Ni̎, L = mhba) also clearly involve phenolate groups in coordination to the metal. A structure for these compounds has been proposed on the basis of spectroscopic and thermogravimetric data. © 1992, Taylor & Francis Group, LLC. All rights reserved.