Benzimidazol-2-ylidene ruthenium complexes for C-N bond formation through alcohol dehydrogenation

Zahid Nawaz; Nevin Gürbüz; Muhammad Naveed Zafar; Namık Özdemir; Bekir Çetinkaya; İsmail Özdemir

doi:10.55730/1300-0527.3606

Benzimidazol-2-ylidene ruthenium complexes for C-N bond formation through alcohol dehydrogenation

Turk J Chem. 2023 Sep 30;47(5):1209-1223. doi: 10.55730/1300-0527.3606. eCollection 2023.

Authors

Zahid Nawaz^{1

2}, Nevin Gürbüz^{2

3

4}, Muhammad Naveed Zafar¹, Namık Özdemir⁵, Bekir Çetinkaya⁶, İsmail Özdemir^{2

3

4}

Affiliations

¹ Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan.
² Catalysis Research and Application Center, İnönü University, Malatya, Turkiye.
³ Department of Chemistry, Faculty of Science and Arts, İnönü University, Malatya, Turkiye.
⁴ Drug Application and Research Center, İnönü University, Malatya, Turkiye.
⁵ Department of Mathematics and Science Education, Faculty of Education, Ondokuz Mayıs University, Samsun, Turkiye.
⁶ Department of Chemistry, Faculty of Science, Ege University, İzmir, Turkiye.

Abstract

A low temperature hydrogen borrowing approach to generate secondary amines using benzimidazole-based N-heterocyclic carbene (BNHC) ruthenium complexes is reported. A series of the piano-stool complexes of the type [(η⁶-p-cymene)(BNHC)RuCl₂] (1a-g) were synthesized via one-pot reaction of the NHC salt precursor, Ag₂O, and [RuCl₂(p-cymene)]₂ and characterized using conventional spectroscopic techniques. The geometry of two precursors, [(η⁶-p-cymene)(^Me4BnMe₂BNHC^CH2OxMe)RuCl₂] (1f) and [(η⁶-p-cymene)(^Me5BnMe₂BNHC^CH2OxMe)RuCl₂] (1g), was studied by single crystal X-ray diffraction. These catalysts were found to dehydrogenate alcohols efficiently at temperatures as low as 50 °C to allow Schiff-base condensation and subsequent imine hydrogenation to afford secondary amines. Notably, this ruthenium-based procedure enables the N-alkylation of aromatic and heteroaromatic primary amines with a wide range of primary alcohols in excellent yields of up to 98%. The present methodology is green and water is liberated as the sole byproduct.

Keywords: Benzimidazol-2-ylidenes; C-N bond formation; amine alkylation; mild conditions; ruthenium complexes.

Grants and funding

Z.N. gratefully acknowledges the Higher Education Commission of Pakistan (HEC) for research funding as an IRSIP fellow at Arizona State University (USA).