Base-free synthesis of benchtop stable Ru(III)-NHC complexes from RuCl ₃ ·3H ₂ O and their use as precursors for Ru(II)-NHC complexes Nida Shahid, Amrendra K. Singh Department of Chemistry, Indian Institute of Technology Indore, India Ru complexes with N -heterocyclic carbene ligands have attracted growing interest in recent years due to wide scope of applications in various fields and tunable stereo-electronic properties. However, even after a few decades of research in this field, a suitable Ru-NHC complex, which can be used as a precursor for synthesis of new complexes with other co-ligands, is still not available. Herein, a base-free route has been discovered for the synthesis of a series of Ru(III)-NHC complexes, identified as [Ru III (PyNHC R )(Cl) 3 (H 2 O)] ( 1a-c ) starting from RuCl 3 ·3H 2 O and bidentate ligand precursors PyNHC R ·HX with R = Me, and i Pr alkyl wingtips. The lewis acidic Ru(III) center seems to operate via a halide-assisted electrophilic C-H activation for the generation of carbene. These structurally simple, benchtop stable complexes are the rare examples of paramagnetic Ru(III)- NHC complexes. Further, complexes 1a-c were shown to be excellent metal precursors for the synthesis of new [Ru II -PyNHC R -PPh 3 ] ( 2a-c ) complexes. All complexes have been characterized using, HRMS, NMR, and UV-vis spectroscopy and molecular structures of 1a , 1b , and 2c have been determined using the single-crystal X-ray diffraction technique. References 1. Q. Zhao, G. Meng, S. P. Nolan and M. Szostak, Chem. Rev. , 2020, 120 , 1981–2048. 2. S. Thota, D. A. Rodrigues, D. C. Crans and E. J. Barreiro, J. Med. Chem. , 2018, 61 , 5805–5821. 3. S. Aghazada, I. Zimmermann, V. Scutelnic and M. K. Nazeeruddin, Organometallics , 2017, 36 , 2397–2403. 4. F. Chen, F. Xiao, W. Zhang, C. Lin and Y. Wu, ACS Appl. Mater. Interfaces , 2018, 10 , 26964–26971. 5. N. Shahid, R. K. Singh, N. Srivastava and A. K. Singh, Dalton Trans. , 2023, 52 , 4176–4185.
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