Synthesis, characterization and behavior in water/DMSO solution of Ru(II) arene complexes with bioactive carboxylates

The reactions of [RuCl(μ-Cl)(η6-p-cymene)]2 with sodium carboxylates, in methanol or acetonitrile solution, afforded the complexes [RuCl(κ2O-RCO2)(η6-p-cymene)] (RCO2 = valproate, 1; aspirinate, 2; diclofenate, 3), in 79–96% yields. Analogously, [RuCl(κ2O-dfCO2)(η6-benzene)], 4, was obtained in admixture with minor by-products from [RuCl(μ-Cl)(η6-benzene)]2 and sodium/silver diclofenate. The sequential reaction of [RuCl(μ-Cl)(η6-p-cymene)]2 with sodium salicylate and PPh3 gave [Ru(κ2O,O′-salCO2)(PPh3)(η6-p-cymene)], 5, in 70% yield. The hydride complex [Ru2Cl2(μ-Cl)(μ-H)(η6-p-cymene)2], 6, was produced in 36% yield from [RuCl(μ-Cl)(η6-p-cymene)]2 and sodium formate. An optimization of the experimental work-up allowed to isolate [RuCl(μ-Cl)(η6-p-cymene)]2 with an improved yield respect to the literature (98% vs. 65%). The bidentate coordination mode of the carboxylato ligands in 1–5 was unambiguously ascertained by IR and NMR spectroscopy, moreover the solid state structure of 1 was elucidated by single crystal X-ray diffraction. Complexes 1–3 experience rapid and quantitative dissociation of the carboxylato anion in DMSO/water/NaCl mixtures, mainly converting into [RuCl2(DMSO)(η6-p-cymene)], 7.