The crystal structure, equlibrium and spectroscopic studies of bis(dialkyldithiocarbamate) copper(II) complexes [Cu_2(R_2dtc)_4] (dtc=dithiocarbamate)

摘要

Four copper(II) complexes of bis(dialkyldithiocarbamate) [Cd(R_2dtc)_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 UV-vis spectrometry in EtOH. were influenced by the alkyl groups in the following order: i-Pr>n-Pr approx= Et>Me. The single crystal structures of complex [Cu_2(R_2dtc)_4] have been determined using X-ray diffraction methods. The compounds [Cu_2(Et_2dtc)_4] and [Cu_2(Pr_2dtc)_4] are built of centrosymmetric neutral dimeric [Cu_2(R_2dtc)_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 occupyring 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_2dtc)_4] is square planar with an exactly planar CuS_4 unit and nearly planar NCS_2 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_2dtc)_4] has the shortest Cu...Cu distance and [Cu(i-Pr_2dtc)_2] has the longest one.