title: Hydrolytic behaviour and chloride ion binding capability of [Ru(η6-p-cym)(H2O)3]2+: a solution equilibrium study.
abstract: Hydrolysis of an organometallic cation, [Ru(η(6)-p-cym)(H(2)O)(3)](2+) (p-cym = 1-isopropyl-4-methylbenzene), in the presence of 0.20 M KNO(3) or KCl as supporting electrolyte was studied in detail with the combined use of pH-potentiometry, (1)H-NMR, UV-VIS and ESI-TOF-MS. Stoichiometry and stability constants of chlorido, hydroxido and mixed chlorido-hydroxido complexes formed in aqueous solution have been determined. At pH < 4.0 where hydrolysis of [Ru(η(6)-p-cym)(H(2)O)(3)](2+) is negligible with increasing chloride ion concentration two chlorido complexes, [Ru(η(6)-p-cym)(H(2)O)(2)Cl](+) and [{Ru(η(6)-p-cym)}(2)(μ(2)-Cl)(3)](+), are detectable. At pH > 5.0, in chloride ion free samples the exclusive formation of [{Ru(η(6)-p-cym)}(2)(μ(2)-OH)(3)](+) is found. However, if chloride ion is present (in the range 0-3.50 M) novel mixed chlorido-hydroxido species, [{Ru(η(6)-p-cym)}(2)(μ(2)-OH)(2)(μ(2)-Cl)](+) and [{Ru(η(6)-p-cym)}(2)(μ(2)-OH)(μ(2)-Cl)(2)](+) can also be identified at pH > 4.0. The results obtained in this study may help in rationalizing the solution behaviour of half-sandwich [Ru(η(6)-p-cym)(XY)Z] type complexes which, after dissociation of both the monodentate Z and the chelating XY, are capable of yielding the free aqua species [Ru(η(6)-p-cym)(H(2)O)(3)](2+). Our results demonstrate that different chloride ion concentrations can influence the speciation in the acidic pH range but at biologically relevant conditions (pH = 7.4, c(Cl(-)) = 0.16 M) and at c(M) = 1 μM [{Ru(η(6)-p-cym)}(2)(μ(2)-OH)(3)](+) is predominant in the absence of any coordinating ligands.
authors: Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4010, Debrecen, Hungary.
authors: Linda
authors: L
authors: Bíró
authors: Etelka
authors: E
authors: Farkas
authors: Péter
authors: P
authors: Buglyó
mesh_terms: D002712:Chlorides / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007477:Ions / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D002712:Chlorides; D056831:Coordination Complexes; D007477:Ions; D009942:Organometallic Compounds; D012428:Ruthenium