Copper hydrotris(3,5-diphenylpyrazolyl)borate dithiocarbamates: mimicking green copper proteins?

New Journal of Chemistry Pub Date: 2014-12-11 DOI: 10.1039/C4NJ01298D

Abstract

Three novel copper hydrotris(3,5-diphenylpyrazolyl)borate (TpPh2) dithiocarbamate complexes, [TpPh2Cu(dtc)] (dtc = S2CNEt21, S2CNBz22 and S2CN(CH2)43) have been prepared in a simple one pot reaction by sequential addition of KTpPh2 and Na(dtc) to CuCl2·2H2O. IR, UV-Vis and ESR spectroscopic studies suggest a mostly κ3 coordinated TpPh2 ligand, bidentate dithiocarbamate ligands and therefore, a five coordinate copper centre. Unusually, a κ3 to κ2 isomerisation of the TpPh2 ligand is found in solution in 3 and to a lesser extent in 1. The X-ray crystal structures reveal geometries intermediate between trigonal bipyramidal and square pyramidal depending on the steric bulk of the dithiocarbamate ligand and a long Cu–N bond resulting in an asymmetrically bound TpPh2 ligand. Electrochemical studies reveal quasi-reversible one-electron oxidation and reduction to Cu(I) with the reversibility and reduction potential strongly dependent on the dithiocarbamate. DFT calculations reveal a weakly antibonding Cu–S π* SOMO and a strongly antibonding Cu–S σ* LUMO consistent with the significant effect of the dithiocarbamate ligand on the electrochemical behaviour of these complexes.

Graphical abstract: Copper hydrotris(3,5-diphenylpyrazolyl)borate dithiocarbamates: mimicking green copper proteins
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