SummaryRuthenium complexes [Ru(L1)2(CH3CN)2](PF6)2 (1), [RuL1(CH3CN)4](PF6)2 (2) and [RuL2(CH3CN)3](PF6)2 (3) (L1= 3-methyl-1-(pyrimidine-2-yl)imidazolylidene, L2 = 1,3-bis(pyridin-2-ylmethyl)benzimidazolylidene) were obtained through a transmetallation reaction of the corresponding nickel–NHC complexes with [Ru(p-cymene)2Cl2]2 in refluxing acetonitrile solution. The crystal structures of three complexes determined by X-ray analyses show that the central Ru(II) atoms are coordinated by pyrimidine- or pyridine-functionalized N-heterocyclic carbene and acetonitrile ligands displaying the typical octahedral geometry. The reaction of [RuL1(CH3CN)4](PF6)2 with triphenylphosphine and 1,10-phenanthroline resulted in the substitution of one and two coordinated acetonitrile ligands and afforded [RuL1(PPh3)(CH3CN)3](PF6)2 (4) and [RuL1(phen)(CH3CN)2](PF6)2 (5), respectively. The molecular structures of the complexes 4 and 5 were also studied by X-ray diffraction analysis. These ruthenium complexes have proven to be efficient catalysts for transfer hydrogenation of various ketones.

Two ruthenium complexes, 3a and 3b, bearing pyrazole-functionalized N-heterocyclic carbenes (NHCs) were prepared, and their structures were characterized by X-ray diffraction analysis. Given their promising anticancer potential, we evaluated the cytotoxicity of both complexes against a panel of human cancer cell lines, including breast cancer Bcap-37, colorectal cancer LoVo, gastric cancer SCG7901, and cisplatinresistant SCG7901-R cells. In vitro results showed that complex 3a inhibited cancer cell proliferation, which exhibited comparable cytotoxicity to that of clinically approved cisplatin. More impressively, complex 3a evoked significant rates of death of [a]

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The asymmetric unit of the title compound, [Co(HCO2)2(C14H12N2)(H2O)]·H2O, contains a mononuclear complex mol­ecule hydrogen bonded to a lattice water mol­ecule. The CoII cation is in a distorted octa­hedral coordination environment defined by the two N atoms of the 2,9-dimethyl-1,10-phenanthroline ligand and four O atoms. Two of these are from a chelating formate anion, one from a monodentate formate and the last from an aqua ligand. In the crystal, mol­ecules are connected by O—H⋯O hydrogen bonds, forming double chains along [100] with the 2,9-dimethyl-1,10-phenanthroline ligands pointing outwards from each chain. These chains are further linked into layers parallel to (011) by inter-chain π–π stacking inter­actions with centroid–centroid distances of 3.61 (1) Å.

Key indicators: single-crystal X-ray study; T = 298 K; mean (C-C) = 0.006 Å; R factor = 0.035; wR factor = 0.118; data-to-parameter ratio = 16.7.