Reversible insertion of Ir into arene ring C-C bonds with improved regioselectivity at a higher reaction temperature

Regioselective metal insertion into aromatic C–C bonds is a long-standing problem critical for development of new arene functionalizations and cleaner conversion of fossil fuel into value-added chemicals. We report reversible insertion of iridium into the aromatic C–C bonds of η4-bound methyl arenes to give eight-membered diiridium metallacycles with yields up to 99%. While at 50–100 °C the reaction yields a mixture of isomers corresponding to iridium insertion in both unsubstituted and Me-substituted ring C–C bonds, at 150 °C a single isomer dominates. Kinetic and DFT studies suggest that at 150 °C insertion of iridium is reversible, allowing equilibration of the metallacycle products via a diiridium arene sandwich complex. The selectivity of metal insertion is determined by the relative stabilities of isomeric metallacycles governed by steric repulsion between methyl groups of the hydrocarbon chain of the cleaved arene and the Cp* ligands

Selective cleavage of unactivated arene ring C-C bonds by iridium: key roles of benzylic C-H activation and metal-metal cooperativity

The cleavage of aromatic C–C bonds is central for conversion of fossil fuels into industrial chemicals and designing novel arene functionalisations through ring opening, expansion and contraction. However, the current progress is hampered by both the lack of experimental examples of selective oxidative addition of aromatic C–C bonds and limited understanding of the factors that favour insertion into the C–C rather than the C–H bonds. Here, we describe the comprehensive mechanism of the only reported chemo- and regioselective insertion of a transition metal into a range of substituted arene rings in simple iridium(i) complexes. The experimental and computational data reveal that this ring cleavage requires both reversible scission of a benzylic C–H bond and cooperativity of two Ir centres sandwiching the arene in the product-determining intermediate. The mechanism explains the chemoselectivity and scope of this unique C–C activation in industrially important methylarenes and provides a general insight into the role of metal–metal cooperativity in the cleavage of unsaturated C–C bonds

From Organometallic Chemistry to Multifunctional Nanoparticle-Based Devices for Gas Detection and Degradation of Air Pollutants

This article was presented at the International Conference EcoBalt 2023 “Chemicals & Environment”, Tallinn, Estonia, 9–11 October 2023, and belongs to the Proceedings of International Conference EcoBalt 2023 "Chemicals & Environment")

Selective <i>ortho</i>-C–H Activation in Arenes without Functional Groups

Aromatic C-H activation in alkylarenes is a key step for the synthesis of functionalised organic molecules from simple hydrocarbon precursors. Known examples of such C-H activations often yield mixtures of products resulting from activation of least-hindered C-H bonds. Here we report highly selective ortho-C-H activation in alkylarenes by simple iridium complexes. We demon-strate that the capacity of the alkyl substituent to override the typical preference of metal-mediated C-H activation for least hindered aromatic C-H bonds results from transient insertion of iridium into the benzylic C-H bond. This enables fast iridium insertion into the ortho-C-H bond, followed by regeneration of the benzylic C-H bond by reductive elimination. Bulkier alkyl substituents increase ortho-selectivity. The described chemistry comprises a conceptually new alternative to existing approaches to aromatic C-H bond activation

Ultra-High-Field 67 Zn and 33 S NMR Studies Coupled with DFT Calculations Reveal the Structure of ZnS Nanoplatelets Prepared by an Organometallic Approach

Herein, we report the successful characterization of sulfur vacancies in ZnS nanoplatelets by in-depth high-field and DNP-enhanced solid-state NMR of 33S and 67Zn nuclei and DFT modeling. This two-dimensional 1 nm-thick nanomaterial was obtained by reacting a dicyclohexyl zinc complex, ZnCy2, with (TMS)2S as the S source under mild conditions (45 °C) in dodecylamine. The joint experimental and theoretical studies on these nanoplatelets evidenced that a large fraction of the Zn and S atoms are located near the surface covered by dodecylamine and that the deviation from stoichiometry (agreeing with energy gap and photoluminescence properties of non-stoichiometric material) is due to sulfur vacancies. Additionally, this work reports the first 33S DNP-NMR spectrum reported in the literature alongside several ultra-high-field 33S and 67Zn solid-state NMR spectra

Understanding unusual element-element bond formation and activation: general discussion

International audienc

Mechanistic insight into organic and industrial transformations: general discussion

International audienc

Mechanistic insight into organic and industrial transformations: general discussion

status: publishe