Cis–trans isomerization of {RuNO}6-type nitrosylruthenium complexes containing 2-pyridinecarboxylate and structural characterization of a μ-H3O2 bridged dinuclear nitrosylruthenium complex

Abstract

cis-[Ru(NO)Cl(pyca)₂] (pyca = 2-pyridinecarboxylate) ([1]), reacts with nucleophiles such as OH⁻ and N₃⁻ in H₂O to generate the dimeric nitrosylruthenium complex, [{Ru(NO)(pyca)₂}₂(μ-H₃O₂)]PF₆·2H₂O ([2]PF₆·2H₂O). The bridging unit of [2]PF₆ is a hydroxide hydrate anion (H₃O₂⁻) composed of a hydroxo and an aqua moiety. Coordinated to each of the ruthenium centers are two pyca ligands in the trans-form with the pyridyl nitrogen atoms and the carboxylic oxygen atoms being at the trans position to each other (trans-form; trans(N,N), trans(O,O)-configuration). [2]PF₆ has also been isolated by the reaction of [1] with N₃⁻ in H₂O. The reaction of [1] with CH₃O⁻ in CH₃OH gives the trans-form nitrosylruthenium complex, trans-[Ru(NO)(OCH₃)(pyca)₂]·CH₃OH (trans(N,N), trans(O,O)-configuration) ([3]·CH₃OH). The rare cis–trans isomerizations have thus occurred during the reaction between [1] (cis-form; trans(N,N), cis(O,O)-configuration) and OH⁻, N₃⁻ or CH₃O⁻.