New square-planar bis(dithiolene) complexes: synthesis, crystallography, and properties of [Bu₄N][M^III(btdt)₂] (M = Cu, Au) and [Bu₄N]₂[Pt^II(btdt)₂] ({btdt}^2- =2,1,3-benzenethiadiazole-5,6-dithiolate)

Abstract

The syntheses, crystal structures, and properties of three new coordination complexes [Bu₄N][M^III(btdt)₂] [M = Cu (1), Au (2)] and [Bu₄N]₂[Pt^II(btdt)₂] (3) ({btdt}^2- = 2,1,3-benzenethiadiazole-5,6-dithiolate) are described. Compounds 1-3 crystallize in a triclinic P-1, and monoclinic P2(1)/c and C2/c space groups, respectively. The {MS4} chromophore lies in almost a square-planar coordination environment in complex 1, but has a slightly distorted square-planar geometry around the central metal ion in compounds 2 and 3. Interactions in the solid state have been studied by intermolecular contacts, in particular, compounds 2 and 3 have been characterized by SN and SS non-covalent interactions among dithiolate complexes, resulting in two- and one-dimensional supramolecular motifs, respectively. Complexes 1-3 show broad absorption bands in the visible region, with that of 3 being sensitive to solvent polarity. Complex 1 exhibits a very low reduction potential for a Cu^III-coordination complex, while the Pt^II complex 3 shows two irreversible oxidative responses at 0.45 V and 0.74 V versus Ag/AgCl, respectively.