Immobilization of pyrene - adorned N - heterocyclic carbene complexes of rhodium (I) on reduced graphene oxide and study of catalytic activity

Twopyrene-tagged N-heterocyclic carbene (NHC) complexes of rhodium(I) wereobtained and characterized. Thetwo complexes were supported onto reduced graphene oxide (rGO), generating two new materials in which the molecular complexes are immob ilized by p–p stacking interactions onto the surfaceofthe 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 catalystcould be effectively recycled up to five times, with negligible loss of activity,whereas the monometallic catalyst rapidlybecame inactive. In the hydrosilylation of terminal alkynes, the selectivity towards the b-(Z)-vinylsilane was improved if the immobilized dimetallic catalyst was used, although the catalyst startedtolose activity after the second run