Kochi first proposed the use of simple iron salts and Grignard reagents for iron-catalyzed cross-coupling reactions in the early 1970s.1 Since the 1970s, iron-catalyzed reactions have become increasingly popular as iron catalysts offer a cheaper and safer alternative to the well studied precious metal catalysts. However, there is limited mechanistic understanding of iron-catalyzed cross-coupling reactions. This gap in knowledge has led to many mechanistic proposals, where the oxidation state of the catalytically relevant species is not agreed upon.2-4 Previous work in the group provides significant evidence for the catalytically relevant iron species, Fe8Me12-, in reactions involving simple iron salts and MeMgBr.5 Characterization of the Fe8Me12- via electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) is consistent with the S = 1/2 species Kochi originally reported.5 These studies help advance the understanding of iron-catalyzed cross-coupling using simple iron salts and MeMgBr, yet there is limited mechanistic understanding when aryl Grignard reagents are used. This presentation will cover current efforts and insight obtained through isolating and characterizing intermediate iron species formed in-situ from simple iron salts and aryl Grignard reagents and evaluating their reactivity towards electrophiles. Characterization techniques include X-ray crystallography, Mössbauer spectroscopy, EPR, MCD, nuclear magnetic resonance (NMR), and gas-chromatography (GC) studies.

Isolation and characterization of in-situ species formed in iron-catalyzed cross-coupling reactions with aryl nucleophiles

255th National Meeting (2018)

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