Synthesis and Reactivity of Thioether-Dithiolate-Bridged Multi-iron Complexes
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The novel thioether-dithiolate-bridged diiron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1, Cp* = η5-C5Me5; tpdt = S(CH2CH2S−)2) has been prepared by the reaction of [Cp*FeCl]2 with Li2(tpdt) in THF. Given the thermodynamic instability of 1, a one-electron oxidation was performed with Fc·PF6 (Fc = ferrocene) affording 1[PF6]. Treatment of 1[PF6] with CO or tBuNC in CH2Cl2 gave complexes [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-CO)}][PF6] (2[PF6]) and [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-tBuNC)}][PF6] (3[PF6]). In addition, complex 1[PF6] can be further oxidized into [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6]2 (1[PF6]2) by Fc·PF6 in THF, while in the presence of MeCN resulting in the formation of complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-MeCN)}][PF6]2 (4[PF6]2). When the solution of complex 1 in THF was warmed to room temperature, thioether-dithiolate-bridged trinuclear iron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*] (5), which can be oxidized into complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2) with Fc·PF6, was obtained accompanied by byproduct Cp*2Fe. Complex 5 is sensitive to air and upon exposure to air in THF gave monoiron complex [Cp*Fe(tpdt)] (6) in moderate yield. Complex 6 is a good metallothiolato precursor for synthesis of homo- and heterobimetallic or trimetallic complexes. The binuclear complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7) can be prepared by the reaction of complex 6 with anhydrous FeCl2 in CH2Cl2. Complex 5[PF6]2 can also be obtained by the reaction of complex 6 with FeCl2 or complex 7 in the presence of NH4·PF6. These complexes have been spectroscopically and crystallographically characterized.
