Catalytic activity and facile recovery of a cyclometalated N-heterocyclic carbene palladium(II) complex immobilized by non-covalent interactions on reduced graphene oxide

The growing concern about the potentially adverse effects of the production of chemical compounds on the sustainable development of the environment has led to a great deal of efforts to search for low-cost and environmentally friendly catalytic systems. A pyrene-tagged N-heterocyclic carbene palladacycle complex ([Pd{(C,N)C6H4CH2NH(Et)}(Imd-P)Br]) was prepared by reacting imidazolium salt with dimer ([Pd-2{(C,N)C6H4CH2NH(Et)}(2)(-OAc)(2)]). Then, it was immobilized onto the surface of reduced graphene oxide (rGO) via - stacking forces. The hybrid compound ((NHC)Pd-rGO) was made in a one-step process. Various techniques were employed to characterize the compound. In addition, computational studies were used to verify the interaction between the Pd complex and rGO. The catalytic activity of the molecular complex and hybrid material was evaluated in both Suzuki-Miyaura cross-coupling reactions and reduction of p-nitrophenol to p-aminophenol. The catalytic activity of the hybrid material was enhanced in comparison with the corresponding homogeneous analogue. Thus, rGO seems to play a significant role in catalytic activity. Hot filtration experiments show the heterogeneous nature of the catalyst resulting from the strong interaction between pyrene and graphene. The hybrid (NHC)Pd-rGO material could be recycled up to six times with no decrease in catalytic activity.