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

Abstract

The novel thioether-dithiolate-bridged diiron complex [Cp*Fe(μ-1 κ 3 SSS ′:2 κ 2 SS -tpdt)FeCp*] ( 1, Cp* = η 5 -C 5 Me 5; tpdt = S(CH 2 CH 2 S − ) 2 ) has been prepared by the reaction of [Cp*FeCl] 2 with Li 2 (tpdt) in THF. Given the thermodynamic instability of 1, a one-electron oxidation was performed with Fc·PF 6 (Fc = ferrocene) affording 1[PF 6 ] . Treatment of 1[PF 6 ] with CO or t BuNC in CH 2 Cl 2 gave complexes [Cp*Fe(μ-1 κ 3 SSS ′:2 κ 2 SS -tpdt){Cp*Fe(η 1 -CO)}][PF 6 ] ( 2[PF 6 ] ) and [Cp*Fe(μ-1 κ 3 SSS ′:2 κ 2 SS -tpdt){Cp*Fe(η 1 - t BuNC)}][PF 6 ] ( 3[PF 6 ] ). In addition, complex 1[PF 6 ] can be further oxidized into [Cp*Fe(μ-1 κ 3 SSS ′:2 κ 2 SS -tpdt)FeCp*][PF 6 ] 2 ( 1[PF 6 ] 2 ) by Fc·PF 6 in THF, while in the presence of MeCN resulting in the formation of complex [Cp*Fe(μ-1 κ 3 SSS ′:2 κ 2 SS -tpdt){Cp*Fe(η 1 -MeCN)}][PF 6 ] 2 ( 4[PF 6 ] 2 ). When the solution of complex 1 in THF was warmed to room temperature, thioether-dithiolate-bridged trinuclear iron complex [Cp*Fe(μ-1 κ 3 SSS ′:2 κ 2 SS -tpdt)Fe(μ-2 κ 2 SS:3 κ 3 SSS ′-tpdt)FeCp*] ( 5 ), which can be oxidized into complex [Cp*Fe(μ-1 κ 3 SSS ′:2 κ 2 SS -tpdt)Fe(μ-2 κ 2 SS:3 κ 3 SSS ′-tpdt)FeCp*][PF 6 ] 2 ( 5[PF 6 ] 2 ) with Fc·PF 6, was obtained accompanied by byproduct Cp* 2 Fe. 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-1 κ 3 SSS ′:2 κ 2 SS -tpdt)FeCl 2 ] ( 7 ) can be prepared by the reaction of complex 6 with anhydrous FeCl 2 in CH 2 Cl 2 . Complex 5[PF 6 ] 2 can also be obtained by the reaction of complex 6 with FeCl 2 or complex 7 in the presence of NH 4 ·PF 6 . These complexes have been spectroscopically and crystallographically characterized.