Synthesis and Reactivity of Thioether-Dithiolate-Bridged Multi-iron Complexes

The novel thioether-dithiolate-bridged diiron complex [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­FeCp*] (<b>1</b>, 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 <b>1</b>, a one-electron oxidation was performed with Fc·PF₆ (Fc = ferrocene) affording <b>1­[PF</b>_<b>6</b><b>]</b>. Treatment of <b>1­[PF</b>_<b>6</b><b>]</b> with CO or ^<i>t</i>BuNC in CH₂Cl₂ gave complexes [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­{Cp*Fe­(η¹-CO)}]­[PF₆] (<b>2­[PF</b>_<b>6</b><b>]</b>) and [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­{Cp*Fe­(η¹-^<i>t</i>BuNC)}]­[PF₆] (<b>3­[PF</b>_<b>6</b><b>]</b>). In addition, complex <b>1­[PF</b>_<b>6</b><b>]</b> can be further oxidized into [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­FeCp*]­[PF₆]₂ (<b>1­[PF</b>_<b>6</b><b>]</b>_<b>2</b>) by Fc·PF₆ in THF, while in the presence of MeCN resulting in the formation of complex [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­{Cp*Fe­(η¹-MeCN)}]­[PF₆]₂ (<b>4­[PF</b>_<b>6</b><b>]</b>_<b>2</b>). When the solution of complex <b>1</b> in THF was warmed to room temperature, thioether-dithiolate-bridged trinuclear iron complex [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­Fe­(μ-2_κ²<i>SS</i>:3_κ³<i>SSS</i>′-tpdt)­FeCp*] (<b>5</b>), which can be oxidized into complex [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­Fe­(μ-2_κ²<i>SS</i>:3_κ³<i>SSS</i>′-tpdt)­FeCp*]­[PF₆]₂ (<b>5­[PF</b>_<b>6</b><b>]</b>_<b>2</b>) with Fc·PF₆, was obtained accompanied by byproduct Cp*₂Fe. Complex <b>5</b> is sensitive to air and upon exposure to air in THF gave monoiron complex [Cp*Fe­(tpdt)] (<b>6</b>) in moderate yield. Complex <b>6</b> is a good metallothiolato precursor for synthesis of homo- and heterobimetallic or trimetallic complexes. The binuclear complex [Cp*Fe­(μ-1_κ³<i>SSS</i>′:2_κ²<i>SS</i>-tpdt)­FeCl₂] (<b>7</b>) can be prepared by the reaction of complex <b>6</b> with anhydrous FeCl₂ in CH₂Cl₂. Complex <b>5­[PF</b>_<b>6</b><b>]</b>_<b>2</b> can also be obtained by the reaction of complex <b>6</b> with FeCl₂ or complex <b>7</b> in the presence of NH₄·PF₆. These complexes have been spectroscopically and crystallographically characterized