Preparation and characterization of metal complexes with an extended TTF dithiolato ligand, bis(propylenedithiotetrathiafulvalenedithiolato)-nickelate and -cuprate

Abstract

Novel monoanionic nickel and dianionic copper complexes with the extended TTF dithiolato ligand, propylenedithiotetrathiafulvalenedithiolate [ptdt^2–=(S₈C₉H₆)^2– ], have been synthesized. Characterization of monoanionic tetraphenylphosphonium and tetramethylammonium salts of Ni(ptdt)₂^– and the dianionic tetraphenylphosphonium salt of Cu(ptdt)₂^2– have been performed, using cyclic voltammetry, electrical resistivity measurements, magnetic susceptibility measurements and X-ray crystal structure determination. The geometries around the Ni atoms are almost square planar. In both Ni complexes, one of the extended ligands of Ni(ptdt)₂^– is overlapping with that of the adjacent anion separated by about half of the unit of the molecule, forming a one-dimensional chain. The adjacent chains are connected by transverse short S‥S contacts. Cu(ptdt)₂^2– has a distorted tetrahedral geometry around the Cu atom and the dihedral angle between the planes of the dithiolato ligand is 54.2 °. The crystal structures of Ni(ptdt)₂^– and Cu(ptdt)₂^2– complexes show the possibility of novel 2D or 3D intermolecular contacts through ptdt ligands. The complex [Me₄N][Ni(ptdt)₂ ]·Me₂CO is a semiconductor with a room temperature conductivity of 1.4×10^–3 S cm^–1 and activation energy of 9.9×10^–2 eV.