Ruthenium−p-cymene complexes with acylthiourea, and its heterogenized form on graphene oxide act as catalysts for the synthesis of quinoxaline derivatives

Abstract

Synthesis of a series of half-sandwich Ru(II) complexes (1-5) containing acylthiourea ligand is reported herein. All the Ru(II) complexes were well characterized by analytical and spectroscopic (UV-Vis, FT-IR, NMR and mass spectrometry) methods. Molecular structures of two (2 and 3) of the complexes were confirmed by single crystal X-ray diffraction, and the complexes adopted pseudo-octahedral geometry around Ru. Catalytic ability of the Ru complexes was evaluated in the synthesis of quinoxaline compounds from various 2-nitroaniline and hydroxy ketone derivatives via transfer hydrogenation approach. Active homogeneous catalyst was heterogenized by supporting it on graphene oxide, and the heterogeneous equivalent was characterized by Raman, XPS, TEM, SEM and ICP-OES techniques. Activity of the heterogeneous catalyst was tested, and it can be reused up to five cycles without any loss in activity.