Development of mixed-ligand ruthenium complexes bearing phosphine and imine ligands for utilisation as catalysts in Suzuki-type C–C cross-coupling reactions

ABSTRACT

Herein we report the development of two mixed-ligand ruthenium (II) complexes bearing phosphine and imine ligands, their thorough characterisation and their utilisation as homogeneous catalysts in Suzuki-type C–C cross-coupling reactions. Reactions of two tetradentate Schiff base ligands, derived from imidazole-2-carboxaldehyde and ethylenediamine (H₂L¹) or propylenediamine (H₂L²), with [Ru(PPh₃)₃Cl₂] in refluxing ethanol in the presence of NEt₃ afforded two complexes of type [Ru(L¹)(PPh₃)₂] and [Ru(L²)(PPh₃)₂], respectively. The solid-state structure of [Ru(L²)(PPh₃)₂] was determined by single crystal X-ray diffraction analysis. The molecular structure of [Ru(L¹)(PPh₃)₂] was optimised by the DFT method. Electronic spectra of the complexes showed intense absorptions spanning over the visible and ultra-violet regions, the origin of which was probed with TDDFT calculations. Redox properties of the complexes were studied by cyclic voltammetry. These mixed-ligand ruthenium(II) complexes serve as efficient catalyst-precursors for Suzuki-type C–C cross-coupling reactions.

GRAPHICAL ABSTRACT

KEYWORDS:

• Tetradentate Schiff base ligands (H₂Lⁿ)
• [Ru(Lⁿ)(PPh₃)₂] complexes
• crystal structures
• electronic spectra
• catalytic C–C cross-coupling

Acknowledgements

The authors express their deepest gratitude to the organisers of the international conference, IICHE-CHEMCON 2023, for giving the platform and an opportunity to publish the work as a conference paper. Financial assistance received from the Department of Science and Technology (DST-SERB), New Delhi [Reference No. CRG/2022/003382], is gratefully acknowledged. The DST-FIST programme of the Department of Chemistry, Jadavpur University, is also gratefully acknowledged for providing infrastructural support. AC thanks the University Grants Commission (UGC), New Delhi, for her fellowship (Ref. No.: 201610133839).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by DST-SERB; DST-FIST; University Grants Commission.