Synthesis of rhodium N-heterocyclic carbene complexes and their catalytic activity in the hydrosilylation of alkenes in ionic liquid medium

Rhodium complexes bearing N-heterocyclic carbene (NHC) ligands were prepared from bis(η4-1,5-cyclooctadiene) dichlorodirhodium and 1-alkyl-3-methylimidazolium-2-carboxylate, and the catalytic properties of rhodium complexes prepared in the hydrosilylation of alkenes in ionic liquid media were investigated. It was found that both the catalytic activity and selectivity of the rhodium complexes bearing NHC ligands were influenced by the attached substituents of the imidazolium cation. Additionally, rhodium complexes bearing NHC ligands in ionic liquid BMimPF6 could be reused without noticeable loss of catalytic activity and selectivity.

Graphical abstractRhodium complexes bearing N-heterocyclic carbene (NHC) ligands were prepared from bis(η4-1,5-cyclooctadiene)dichlorodirhodium and 1-alkly-3-methylimidazolium-2-carboxylate, and it was found that both the catalytic activity and selectivity of the rhodium complexes bearing NHC ligands were influenced by the attached substituents of the imidazolium cation in the hydrosilylation of alkenes in ionic liquid media.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A series of 1-alkyl-3-methylimidazolium-2-carboxylate synthesized by 1-alkylimidazole and dimethyl carbonate are obtained. ► High levels of conversion and selectivity were obtained with Rh–NHC/BMimPF6 system. ► Both the catalytic activity and selectivity of the rhodium complexes bearing NHC ligands were influenced by the attached substituents of the imidazolium cation. ► Rhodium complexes bearing NHC ligands in ionic liquid BMimPF6 could be reused without noticeable loss of catalytic activity and selectivity.