Syntheses and electrochemical characterization of heteroleptic cyclopentadienyl-dithiolene d2 tungsten complexes.: Structures and magnetic properties of charge-transfer salts

Novel diamagnetic tungsten(IV) complexes of general formula W(eta-C5H4R)(2)(dithiolene) [R = H, SiMe3 or Bu-t; dithiolene = C3S52-(4,5-disulfanyl-1,3-dithiole-2-thionate), C3OS42- (4,5-disulfanyl-1,3-dithiole-2-onate) or dddt(2-) (5,6-dihydro-1,4-dithiine-2,3-dithiolate)] have been synthesized and their redox properties investigated by cyclic voltammetry. Two reversible oxidation waves are observed for each complex. The redox half-wave potentials allow [W(cp)(2)(dddt)] (cp = eta-C5H5) to react with the organic acceptor tcnq (tetracyanoquinodimethane) while the C3S52- and C3OS42- compounds reduce tcnqf(4) (7,7,8,8-tetracyano-1,2,4,5-tetrafluoroquinodimethane). X-Ray crystallographic studies were carried out on [W(cp)(2)(dddt)](.+)[tcnq](.-) and [W(eta-C5H4But)(2)(C3S5)](.+)[tcnqf(4)](.-). The structural analyses and extended-Huckel calculations showed that the radical anions are strongly dimerised into diamagnetic moieties. The cations form centrosymmetrical dimers and exhibit antiferromagnetic interactions, as deduced from the temperature dependence of the magnetic susceptibility, with T(chi(max)) = 18 and 22 K for [W(cp)(2)(dddt)](.+)[tcnq](.-) and [W(eta-C5H4But)(2)(C3S5)](.+)[tcnqf(4)](.-) respectively.