Catalytic N-oxidation of tertiary amines on RuO2NPs anchored graphene nanoplatelets

Abstract

Ultrafine ruthenium oxide nanoparticles (RuO₂NPs) with an average diameter of 1.3 nm were anchored on graphene nanoplatelets (GNPs) using a Ru(acac)₃ precursor by a very simple dry synthesis method. The resultant material (GNPs–RuO₂NPs) was used as a heterogeneous catalyst for the N-oxidation of tertiary amines for the first time. The transmission electron microscopy (TEM) images of the GNPs–RuO₂NPs showed the excellent attachment of RuO₂NPs on GNPs. The loading of Ru in GNPs–RuO₂NPs was 2.68 wt%, as confirmed by scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). The X-ray photoelectron spectrum (XPS) and the X-ray diffraction pattern (XRD) of GNPs–RuO₂NPs revealed that the chemical state of Ru on GNPs was +4. After the optimization of reaction conditions for N-oxidation of triethylamine, the scope of the reaction was extended to various aliphatic, alicyclic and aromatic tertiary amines. The GNPs–RuO₂NPs showed excellent catalytic activity in terms of yields even at a very low amount of Ru catalyst (0.13 mol%). The GNPs–RuO₂NPs was heterogeneous in nature, chemically as well as physically, very stable and could be reused up to 5 times.