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

Abstract

Metal complexes of 2,6-dimethoxybenzoic acid (Hdmba), [M(dmba)₂(H₂O)₃]·H₂O, for M = Mn^II, Co^II, Ni^II, or Zn^II 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.