Charu Sharma1, Avinash Kumar Srivastava1, Kamal Nayan Sharma2, Raj Kumar Joshi1. 1. Department of Chemistry, Malaviya National Institute of Technology, Jaipur - 302017, Rajasthan, India. rkjoshi.chy@mnit.ac.in. 2. Department of Chemistry, Amity School of Applied Sciences, Amity University Haryana, Manesar, Gurugram 122413, Haryana, India. kamalnayaniitd@gmail.com.
Abstract
Three new pyrazolated chalcogenoether ligated Rh(iii) half-sandwich complexes (1-3) were synthesised by the thermal reaction of chalcogenoether (S, Se and Te) substituted 1H-pyrazole ligands (L1-L3) and [(η5-C5Me5)RhCl]2 in methanol. The complexes were fully characterised by various spectroscopic techniques, and the molecular structures of complexes 1 and2 were also established through single crystal X-ray crystallographic analysis, which indicates a pseudo-octahedral half-sandwich piano-stool geometry around the rhodium metal. All three complexes were found to be thermally stable and insensitive towards air and moisture. One mol% of Rh(iii) complexes (1-3) along with 10 mol% of Cu(OAc)2 were explored for the Buchwald-Hartwig type C-N coupling reactions of amine and aryl chloride. Good to excellent yields (89-92%) of the coupling products were obtained with seleno- and thio-ether functionalised pyrazolated Rh(iii) complexes (1 and 2), while an average yield (39%) was obtained with the telluro-ether functionalised complex (3). In contrast to the previously reported C-N coupling reactions the present reaction works under solvent- and base-free conditions, and the coupling reaction is accomplished in just 6 h with a high yield of the coupling product. The present methodology was also found to be efficient for a wide variety of functionalised aryl halides, and aliphatic or aromatic amines (1° and 2°). Moreover, the reaction also enables the C-N coupling of electron-withdrawing substrates and base-sensitive functionalities.
Three new pyrazolated chalcogenoether ligated Rh(iii) half-sandwich complexes (1-3) were synthesised by the thermal reaction of chalcogenoether (S, Se and Te) substituted n class="Chemical">1H-pyrazole ligands (L1-L3) and [(η5-C5Me5)RhCl]2 in methanol. The complexes were fully characterised by various spectroscopic techniques, and the molecular structures of complexes 1 and2 were also established through single crystal X-ray crystallographic analysis, which indicates a pseudo-octahedral half-sandwich piano-stool geometry around the rhodium metal. All three complexes were found to be thermally stable and insensitive towards air and moisture. One mol% of Rh(iii) complexes (1-3) along with 10 mol% of Cu(OAc)2 were explored for the Buchwald-Hartwig type C-N coupling reactions of amine and aryl chloride. Good to excellent yields (89-92%) of the coupling products were obtained with seleno- and thio-ether functionalised pyrazolated Rh(iii) complexes (1 and 2), while an average yield (39%) was obtained with the telluro-ether functionalised complex (3). In contrast to the previously reported C-N coupling reactions the present reaction works under solvent- and base-free conditions, and the coupling reaction is accomplished in just 6 h with a high yield of the coupling product. The present methodology was also found to be efficient for a wide variety of functionalised aryl halides, and aliphatic or aromatic amines (1° and 2°). Moreover, the reaction also enables the C-N coupling of electron-withdrawing substrates and base-sensitive functionalities.