Synthesis and Structural Characterization of Half-Sandwich Arene–Ruthenium(II) Complexes with Bis(imidazol-1-yl)methane, Imidazole and Benzimidazole

Abstract

Mono- and binuclear arene–ruthenium(II) complexes with imidazole-containing ligands were prepared by the reaction of the ligands (L1 = bis(imidazole-1-yl)methane; ImH = 1H-Imidazole; BImH = 1H-Benzimidazole) with [(p-cym)Ru(µ-Cl)2]2 dimers. When bis(imidazole-1-yl)methane reacted with [(p-cym)Ru(µ-Cl)2]2 in methanol, a binuclear complex of the type [Ru2(L1)2(p-cym)2Cl2]Cl2 (2) with cyclic structure was synthesized, whereas by using acetonitrile as a solvent under the same reaction conditions, an unexpected C–N bond cleavage was observed, and a complex of formula [Ru(ImH)2(p-cym)Cl]Cl (1) with coordinated imidazole molecules was obtained. Another type of arene–ruthenium complex [Ru(BImH)(p-cym)Cl2] (3) was obtained by the reaction of benzimidazole and [(p-cym)Ru(µ-Cl)2]2. All compounds were characterized by spectral (FT-IR, NMR 1H, 13C) and single-crystal X-ray diffraction methods; their catalytic activity in transfer hydrogenation and the cytotoxicity against MCF-7 and HepG2 cells were evaluated.

Synthesis, Characterization and Biological Investigations of Half-Sandwich Ruthenium(II) Complexes Containing Benzimidazole Moiety

“…The bond distance of Ru-N is short, with a value of 2.112(2) Å. This parameter is similar to that found in other arene Ru(II) complexes having a benzimidazole ligand [41,42]. Moreover, the benzimidazole C-C bond distances become more inequivalent, with C4-C5 and C6-C7 (~1.375 Å) shorter than the other one C5-C6 (1.413 Å) and the other three C-C bonds (C4-C9, C8-C9, C7-C8) that are in between (~1.399 Å) suggesting electron delocalization in the ligand.…”

“…Figure 2a for complex 2 shows that the Ru(II) ion is coordinated with one monodentate ligand (bim), one arene and two chloride ions giving rise to a {RuNC 3 Cl 2 } chromophore. The similar structure of the arene complex was reported by Matveeevskaya [41] but with a different synthesis procedure and X-ray measurement conditions. The structural analysis confirmed the presence of bim that was generated by the decarboxylation of benzimidazole-2-carboxylic acid.…”

“…The results obtained in both the MTS assay and flow cytometry showed that the tested ruthenium complexes in the concentration range of 30 to 1000 µM are neither cytotoxic to A549 lung cancer cells nor to normal VH10 skin cells (IC 50 above 1000 µM) (Figure S2, Table S4). Two other research teams also studied the cytotoxic activity of the ruthenium-benzimidazole complex [41,46]. The Ru complex, synthesized by scientists from Russia, was evaluated against human breast adenocarcinoma (MCF-7) and human hepatocellular carcinoma (HepG2) cell lines [41].…”

Ruthenium(II) Tris‐Pyrazolylmethane Complexes in Transfer Hydrogenation Reactions

“…In 2020, the reduction of ketones mediated by ruthenium(II) p ‐cymene complexes, containing quinoxalin‐11‐one derivatives or tryptanthrin‐6‐oxime, was reported by Potapov and Benassi, resulting in moderate to excellent yields with 2‐propanol as the hydrogen donor [32] . Subsequently, the same group successfully synthesized a series of mono‐ and dinuclear arene‐ruthenium (II) complexes with imidazole‐containing ligands and applied them as efficient catalysts in the TH reaction [33] . In spite of these relatively recent developments, the exploration of novel catalysts and mechanistic features remains of high interest.…”

“…[32] Subsequently, the same group successfully synthesized a series of mono-and dinuclear arene-ruthenium (II) complexes with imidazole-containing ligands and applied them as efficient catalysts in the TH reaction. [33] In spite of these relatively recent developments, the exploration of novel catalysts and mechanistic features remains of high interest.…”