Iron tris-mesityl: a homoleptic iron(ii) ferrate species for directed C–H activation

Abstract

C–H activation is a vital synthetic tool due to its superior atom economy and improved step efficiency making it amendable to late-stage functionalisation. In recent years iron has been gaining traction within this field due to its high abundance, low cost and low toxicity. Iron(0) phosphines for C–H activation via oxidative addition are well documented, however, only a handful of iron(II) complexes competent at C–H activation via ligand-to-ligand hydrogen atom transfer (LLHT) or σ-bond metathesis have been identified. Herein we report the first homoleptic iron species capable of facilitating C–H activation, introducing a new class of well-defined iron(II) complexes for this purpose, and detail the synthesis and characterisation of a range of tris-cyclometalated iron complexes using a variety of pyridine derived substrates. Density functional theory (DFT) calculations reveal that the C–H activation proceeds through a σ-bond metathesis pathway.