The crystal structure, equilibrium and spectroscopic studies of bis(dialkyldithiocarbamate) copper(II) complexes [Cu2(R2dtc)4] (dtc=dithiocarbamate)

Four copper(II) complexes of bis(dialkyldithiocarbamate) [Cd(R(2)dtc)(2)] (R=Me, Et, Pr, i-Pr; dtc=dithiocarbamate) have been prepared and characterized by elemental analysis, IR and ESR spectra studies. Their equilibrium constants (K), determined by a W-vis spectrometry in EtOH, were influenced by the alkyl, groups in the following order: i-Pr>n-Pr approximate to Et>Me. The single crystal structures of complex [Cu-2(R(2)dtc)(4)] have been determined using X-ray diffraction methods. The compounds [Cu-2(Et(2)dtc)(4)] and [Cu-2(Pr(2)dtc)(4)] are built of centrosymmetric neutral dimeric [Cu-2(R(2)dtc)(4)] entities. The copper atom lies in a distorted square-pyramidal environment. The four equatorial donors are two bidentate chelate sulfur atoms from two dtc ligands. One of-the sulfur atoms from the third dtc ligand acts as a bridging ligand occupying the apical position of the symmetry-related copper atom in the dimer structure, which is viewed as two edge-sharing distorted square-pyramids. The structure of [Cu-2(i-Pr(2)dtc)(4)] is square planar with an exactly planar CuS4 unit and nearly planar NCS2 moieties. The Cu-S distances shows small decreases along the series n-Pr>Et>i-Pr, the biggest change being for the diisopropyl complex. The alkyl substituents at the nitrogen atom affect their coordination number and Cu Cu distance. In the solid, [Cu-2(n-Pr(2)dtc)(4)] has the shortest Cu ... Cu distance and [Cu(i-Pr(2)dtc)(2)] has the longest one. (C) 1999 Elsevier Science Ltd. Ail rights reserved.