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

Abstract

The thioether-dithiolate-bridged heterotrinuclear complexes [Cp*Fe(μ-1_k³SSS′:2_k²SS-tpdt)M(μ-2_k²SS:3_k³SSS′-tpdt)FeCp*][PF₆]₂ (Cp* = η⁵-C₅Me₅; tpdt = S(CH₂CH₂S)₂; 2, M = Co; 3, M = Ni; 4, M = Pd) have been prepared by a reaction of [Cp*Fe(η³-tpdt)] (1) with complexes CoCl₂, NiCl₂(PPh₃)₂, and PdCl₂(PPh₃)₂, respectively. Similarly, treatment of complex 1 with CuCl(PPh₃) or AgPF₆ afforded two heterotrinuclear complexes, [Cp*Fe(μ-1_k³SSS′:2_k²SS-tpdt)M(μ-2_k²SS:3_k³SSS′-tpdt)FeCp*][PF₆] (5, M = Cu; 6, M = Ag), while reaction of 1 with the complex AuCl(PPh₃) gave a heterobinuclear complex, [Cp*Fe(μ-1_k³SSS′:2_k¹S-tpdt)Au(PPh₃)][PF₆] (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_eff 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.