Synthesis, structure and physical properties of transition metal bis 4-cyanobenzene-1,2-dithiolate complexes [M(cbdt)2]z− (M = Zn, Co, Cu, Au, Ni, Pd, z = 0, 1, 2)

Abstract

A series of new [M(cbdt)2]z− complexes of the 4-cyanobenzene-1,2-dithiolate (cbdt) ligand with a range of transition metals M (M=Zn, Co, Cu, Au, Ni, Pd) were prepared in different oxidation states (z=0, 1, 2) as salts with several cations and characterised by X-ray diffraction, cyclic voltammetry, EPR and static magnetic susceptibility. Their properties are discussed in comparison either with the Fe analogue or corresponding complexes based on the dicyano substituted ligand (dcbdt) previously described by us. These complexes can be prepared either from the ligand dithiol as previously described for the Fe analogue, or in a more convenient way to obtain the more reduced forms, from the 4-cyanobenzene-1,3-dithiole-2-thione (1) which is described here for the first time. The structure of these complexes presents square planar coordination geometry, and belong to four distinct groups: (i) the Au monoanionic compound 4a is monoclinic, C2/c, where the complex presents a cis–trans disorder; (ii) the compounds 10b, 7b of the dianionic Pd and Ni complexes, are isostructural, monoclinic, P21/c, with the metal in an inversion centre, a perfect square-planar coordination geometry and a ligand trans configuration; (iii) the compounds (8a and 9a) of the Co and Cu dianionic complexes, which are monoclinic P21, with the metal located in a general position with square planar coordination and ligand trans configuration; and (iv) the monoanionic Cu compound 12 is triclinic, P1¯, with the metal in a general position with almost ideal square-planar coordination and ligand trans configuration. These complexes present redox properties intermediate between those based on dcdbt and unsubstituted benzenedithiolate ligand (bdt), and the gold complex can be obtained in the neutral state. The EPR and static magnetic susceptibility measurements show that the dianionic cobalt and copper complexes (8a and 9a) the monoanionic nickel (3), and the neutral gold (11) complexes are paramagnetic corresponding to an S=½ state. The powder EPR spectrum of the dianionic Co complex 8a presents a hyperfine structure typical of I=7/2 59Co with a component a0x=8.6mT.