Synthesis, crystal structure and acidic properties in aqueous solution of phosphate ammine complexes of ruthenium nitrosyl

First examples of phosphate ammine complexes of ruthenium nitrosyl trans-[Ru(NO)(NH3)(4)(HxPO4)] (NO3)(x) (2 - x) H2O (x = 0, 1, 2) were obtained with good yields. Results of elemental analysis, X-ray, infrared, UV-Vis diffuse reflectance, and P-31 NMR spectroscopies fit well with the formulas [Ru(NO)(NH3)(4)(PO4)]center dot 2H(2)O (1), [Ru(NO)(NH3)(4)(HPO4)]NO3 center dot H2O (2), and [Ru(NO)(NH3)(4)(H2PO4)](NO3)(2) (3). In all the complexes, the phosphate group is in a trans-position to NO and is monodentate coordinated to ruthenium by one of the oxygen atoms. The pK(a) values 2.6 and 7.2 were calculated from potentiometric titration and P-31 NMR for the reactions: trans-[Ru(NO)(NH3)(4)(H2PO4)](2+) + H2O reversible arrow trans-[Ru(NO)(NH3)(4) (HPO4)](+) + H3O+ and trans-[Ru(NO)(NH3)(4)(HPO4)](+) + H2O reversible arrow trans-[Ru(NO)(NH3)(4)(PO4)] + H3O+, respectively. The rate constant for the reaction trans-[Ru(NO)(NH3)(4)(H2O)](3+) + H2PO4 reversible arrow trans-[Ru(NO)(NH3)(4) (H2PO4)](2+) + H2O was estimated as k(obs) = 7 x 10 (8) s (1) at 70 degrees C in a dilute solution of H3PO4(similar to 5 M). (c) 2014 Elsevier B.V. All rights reserved.