Synthesis and structure characterization of [Co(H₂O)₂(DMSO)₂(4-nba)]4-nba (DMSO = dimethylsulfoxide; 4-nba=4-nitrobenzoate)

Dissolution of a fine powder obtained by mechanochemical grinding of cobaltous carbonate with 4-nitrobenzoic acid (4-nbaH) in hot dimethylsulfoxide (DMSO) followed by slow evaporation of the solvent resulted in the formation of cis-diaquabis(dimethylsulfoxide)4-nitrobenzoatocobalt(II) 4-nitrobenzoate 1 in good yield. The title compound [Co(H2O)(2)(DMSO)(2)(4-nba)]4-nba 1 crystallizes in the centrosymmetric monoclinic P2(1)/c space group. The structure of 1 consists of two crystallographically independent Co(II) ions. Each unique cobalt exhibits octahedral geometry and is bonded to a pair of terminal aqua ligands situated cis to each other and a bidentate 4-nba ligand which form the square base of the octahedron. A pair of DMSO ligands disposed trans to each other complete the hexa coordination around the central metal. The [Co(H2O)(2)(DMSO)(2) (4-nba)](+) cations and the 4-nba anions are interlinked with the aid of several weak H-bonding interactions. A comparative study of several 4-nitrobenzoate compounds of cobalt is described.