Sulfur-Centered Reactivity of Oxidized Iron-Thiolate Complex toward Unsaturated Hydrocarbon Addition

Abstract

The sulfur-based reactivity of transition-metal thiolate complexes toward alkenes has received extensive attention as a significant proposal for a potential olefin purification scheme. The one-electron oxidation of half-sandwich iron thioether-dithiolate complex [Cp*Fe(η3-tpdt)] (1, Cp* = η5-C5Me5; tpdt = S(CH2CH2S–)2) resulted in the formation of iron-stabilized thiyl radicals, which can interact with unsaturated hydrocarbons such as alkenes or alkynes to give the corresponding trithioether-iron adducts. Interestingly, during this transformation process, the formal oxidation state of the iron center changed from +IV to +II, which suggests a two-electron transfer from unsaturated hydrocarbons to the iron center. Furthermore, the electrochemical measurements reveal this C–S bond formation is an irreversible process, during which ethylene cannot release under electrochemical reductive conditions. These adducts were unambiguously identified by various spectroscopic and X-ray crystallographic characterizations.