Square-planar complexes of pentane-2,4-dithione (dithioacetylacetone): crystal structures of the cobalt(II) and nickel(II) derivatives

Abstract

The crystal and molecular structure of the cobalt(II) and nickel(II) derivatives of dithioacetylacetone (sacsacH) have been determined by X-ray diffraction methods. Both crystals, being isomorphous, are orthorhombic, with space group Cmca and Z= 4. For Co(sacsac)₂: a= 15·64(2), b= 14·35(2), and c= 6·05(1)Å; for Ni(sacsac)₂: a= 15·592(6), b= 14·348(8), and c= 5·950(3)Å. The cobalt(II) structure was solved by conventional Patterson and Fourier methods and was refined by a least-squares method to R 0·11 for 437 independent reflections derived by photographic methods. For the nickel structure, 585 independent reflections, collected by counter methods, were used and the structure refined, by least squares, to R 0·044. The crystals are molecular with discrete monomeric molecular units of composition M (sacsac)₂. Each metal atom, located a site of symmetry 2/m, is precisely coplanar with the four sulphur atoms bonded to it and, with an S–M–S intraligand bond angle of ca. 97°, the metal environment is conveniently described as square planar. However, the molecule as a whole is not planar being folded so that the dihedral angle between the MS₄ and the ligand planes is ca. 6°. The metal–sulphur bond distance is ca. 2·17 Å.