Immobilization of Pyrene‐Adorned N‐Heterocyclic Carbene Complexes of Rhodium(I) on Reduced Graphene Oxide and Study of their Catalytic Activity

Abstract

AbstractTwo pyrene‐tagged N‐heterocyclic carbene (NHC) complexes of rhodium(I) were obtained and characterized. The two complexes were supported onto reduced graphene oxide (rGO), generating two new materials in which the molecular complexes are immobilized by π–π stacking interactions onto the surface of the solid. The catalytic activity of both complexes and solid hybrid materials were studied in the 1,4‐addition of phenylboronic acid to cyclohex‐2‐one, and in the hydrosilylation of terminal alkynes. The studies showed that for both reactions, the dimetallic complex displayed better catalytic performances than the monometallic one. This accounted for both the reactions performed in homogeneous conditions and for the reactions performed with the solid. In the case of the addition of phenylboronic acid to cyclohexanone, the solid containing the dimetallic catalyst could be effectively recycled up to five times, with negligible loss of activity, whereas the monometallic catalyst rapidly became inactive. In the hydrosilylation of terminal alkynes, the selectivity towards the β‐(Z)vinylsilane was improved if the immobilized dimetallic catalyst was used, although the catalyst started to lose activity after the second run.