Comparative structural description of five arene ruthenium(II) complexes of N , N -bidentate Schiff base ligands to rela
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Comparative structural description of five arene ruthenium(II) complexes of N,N‑bidentate Schiff base ligands to related complexes from literature Joel M. Gichumbi1,2 · Holger B. Friedrich2 · Bernard Omondi3 Received: 28 May 2020 / Accepted: 31 July 2020 © Springer Nature Switzerland AG 2020
Abstract A series of new half-sandwich Ru(II) complex salts of the general formula [(η6-arene)RuX(L)]PF6 (where arene = p-cymene, X = Br and ligand L1 = N-tert-butyl-N-(pyridyl methylene) amine (complex 1), ligand L2 = N-isopropyl-2-pyridine carbaldimine (complex 2), ligand L3 = (2,5-dimethyl-phenyl)-pyridin-2-yl methylene amine (complex 3), ligand L4 = (3,5-dimethyl-phenyl)-pyridin-2-yl methylene (complex 4) and arene = C6H6, X = I, ligand L5 = (4-bromo-phenyl)-pyridin-2-yl methylene (complex 5) have been synthesized by reacting the ruthenium arene precursors [(η6-arene)Ru(μ-X)X]2 with N,N-bidentate ligands in a 1:2 ratio. Full characterization of the complexes was accomplished by physicochemical and spectroscopic methods and X-ray structures of all the complexes 1–5. The crystal structures reveal that the ruthenium centers in 1–5 are coordinated to the N,N-bidentate ligand in a bidentate manner, to the respective halide, and to the arene ring to give a pseudo-tetrahedral geometry around them. The whole arrangement is referred to as the three-legged piano stool, in which the N,N-bidentate ligand and the halide (Br or I) serve as the base occupying three coordination sites, while the arene ring serves as the apex of the stool and occupy the remaining coordination sites.
Introduction Half-sandwich arene ruthenium(II) complexes represent one of the most sought after organometallic compounds due to their potential applications in many areas [1]. The complexes have found applications in catalysis, including transfer hydrogenation of ketones [2], oxidation of alcohols [4], and styrene [5] ring-closing olefin metathesis [6] and as asymmetric catalysts for Diels–Alder reactions [7]. Besides, several half-sandwich Ru(II) compounds show promising antimicrobial and anticancer activity [8–11]. Half-sandwich ruthenium complexes have also been applied as catalysts for C–C and C-heteroatom bond formation through direct C–H * Bernard Omondi [email protected] 1
Department of Physical Science, Chuka University, P.O Box 109‑60400, Chuka, Kenya
2
School of Chemistry and Physics, Westville Campus, University of KwaZulu-Natal, Private Bag X54001, Durban 4001, South Africa
3
School of Chemistry and Physics, Pietermaritzburg Campus, University of KwaZulu-Natal, Private Bag X01, Pietermaritzburg 3209, South Africa
bond activation [12], C–N bond formation [13] and reduction of nitro arenes [14]. Arene ruthenium complexes continue to attract a lot of interest in organometallic chemistry because they require mild conditions for their synthesis, give high yields, and are stable and soluble under aqueous conditions [1]. Research has shown that the nature of the arene, the chelating ligands, and the leaving group in the complexes strongly
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