We report an unprecedented selective cleavage of aromatic C-C bonds through the insertion of well-defined iridium complexes into the aromatic ring of simple alkylarenes. The insertion occurs at 50-100 °C without the activation of weaker C-H and C-C bonds and gives unique metallacycles in high yields. Key to the success of this approach is metal-induced deformation of the arene ring, which creates temporary ring strain and promotes direct and selective insertion of the metal into the otherwise inert arene ring C-C bonds.

This work describes the development of easy to prepare cobalt nanoparticles (NPs) in solution as promising alternative catalysts for alkene hydrosilylation with the industrially relevant tertiary silane MD H M (1,1,1,3,5,5,5-heptamethyltrisiloxane). The Co NPs demonstrated high activity when used at 30 °C for 3.5-7 h in toluene, with catalyst loadings 0.05-0.2 mol%, without additives. Under these mild conditions, a set of terminal alkenes were found to react with MD H M, yielding exclusively the anti-Markovnikov product in up to 99% yields. Additionally, we demonstrated the possibility of using UV irradiation to further activate these cobalt NPs in order to enhance their catalytic performances, but also to promote tandem isomerization-hydrosilylation reactions using internal alkenes, among them unsaturated fatty ester (methyl oleate), to produce linear products in up to quantitative yields.

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 η 4 -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.