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

TL;DR

Scientists developed a new iron compound that efficiently activates carbon-hydrogen bonds, offering a sustainable and cost-effective approach for chemical synthesis.

Contribution

The first homoleptic iron(II) complex capable of directed C–H activation is introduced.

Findings

FeMes3− facilitates C–H activation via σ-bond metathesis.

Tris-cyclometalated iron complexes are synthesized using pyridine-derived substrates.

DFT calculations confirm the σ-bond metathesis pathway for 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.

The homoleptic organoferrate complex FeMes3− is identified as an effective iron(ii) species for directed C–H activation, yielding tris-cyclometalated iron products.

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