Synthesis, structure, and spectroscopic and magnetic properties of catena-μ-aqua-diaquabis(2,6-dimethoxybenzoato)metal(II) monohydrate complexes of manganese, cobalt, nickel, and zinc. X-Ray crystal structure of [Co(dmba)2(H2O)3]·H2O

Metal complexes of 2,6-dimethoxybenzoic acid (Hdmba), [M(dmba)2(H2O)3]·H2O, for M = MnII, CoII, NiII, or ZnII have been prepared and studied by means of X-ray diffraction, electronic and i.r. spectroscopies as well as magnetic measurements. The crystal and molecular structure of the cobalt complex has been determined by single-crystal X-ray diffraction and refined by least-squares methods to R = 0.0347 on the basis of 1 337 independent significant counter data. Crystals are orthorhombic, space group Pna21, with unit-cell dimensions a = 7.934(3), b = 10.652(3), c = 26.423(7) Å, and Z = 4. The compound is polymeric, the metal atoms being linked to each other by bridging water molecules to form an infinite chain. The metal ion is six-co-ordinate, the equatorial ligands being two mutually trans water molecules and two unidentate carboxylate groups of the dmba anions. The metal-oxygen bonds in the bridge [2.165(4) and 2.172(4) Å] are longer than the other metal-oxygen distances [M-O(water) 2.091(7) and 2.033(8) Å; M-O(carboxy) 2.073(5) and 2.069(5) Å] giving rise to a tetragonally distorted octahedron at the metal ion. The intra-chain Co-Co distance along the a axis is 3.97 Å, whereas the shortest inter-chain distances along the b and c axes are 10.65 and 14.28 Å, respectively. The Mn, Ni, and Zn complexes are isomorphous with the cobalt compound. Magnetic susceptibility data, in the range 4.2-300 K, for the Co, Ni, and Mn complexes are reported and discussed in relation to the structural data.