Synthesis and characterization of a family of thioether-dithiolate-bridged heteronuclear iron complexes.

The thioether-dithiolate-bridged heterotrinuclear complexes [CpFe(μ-1SSS':2SS-tpdt)M(μ-2SS:3SSS'-tpdt)FeCp][PF] (Cp* = η-CMe; tpdt = S(CHCHS); 2, M = Co; 3, M = Ni; 4, M = Pd) have been prepared by a reaction of [CpFe(η-tpdt)] (1) with complexes CoCl, NiCl(PPh), and PdCl(PPh), respectively. Similarly, treatment of complex 1 with CuCl(PPh) or AgPF afforded two heterotrinuclear complexes, [CpFe(μ-1SSS':2SS-tpdt)M(μ-2SS:3SSS'-tpdt)FeCp*][PF] (5, M = Cu; 6, M = Ag), while reaction of 1 with the complex AuCl(PPh) gave a heterobinuclear complex, [Cp*Fe(μ-1SSS':2S-tpdt)Au(PPh)][PF] (7). These complexes have been spectroscopically and crystallographically characterized. An X-ray diffraction analysis showed that complexes 2, 3, 5, and 6 feature a heterometal center binding four sulfur atoms of two tpdt ligands with a cis orientation. However, in the Pd-containing complex 4, two tpdt ligands are arranged in a trans configuration. The μ data and EPR results indicate that complexes 2, 4, 5, 6, and 7 are paramagnetic and only complex 3 is diamagnetic. Electrochemical experiments on these heteronuclear clusters were performed at room temperature. Discrepancy of the redox couples in the CV plots of these complexes indicates different one-electron transfer processes.