Abstract

Three novel copper hydrotris(3,5-diphenylpyrazolyl)borate (Tp^Ph2) dithiocarbamate complexes, [Tp^Ph2Cu(dtc)] (dtc = S<inf>2</inf>CNEt<inf>2</inf>1, S<inf>2</inf>CNBz<inf>2</inf>2 and S<inf>2</inf>CN(CH<inf>2</inf>)<inf>4</inf>3) have been prepared in a simple one pot reaction by sequential addition of KTp^Ph2 and Na(dtc) to CuCl<inf>2</inf>·2H<inf>2</inf>O. IR, UV-Vis and ESR spectroscopic studies suggest a mostly κ³ coordinated Tp^Ph2 ligand, bidentate dithiocarbamate ligands and therefore, a five coordinate copper centre. Unusually, a κ³ to κ² isomerisation of the Tp^Ph2 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 Tp^Ph2 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.