The rate of hydrolysis of (NH 4) 2RuNOCl 5 and (NH 4) 2RuNOCl 4OH

Abstract

The rates of hydrolysis of (NH 4) 2RuNOCl 5 and (NH 4) 2RuNOCl 4OH have been measured at an ionic strength of 0.50 over a wide range of temperatures and pH. All reactions studied were first order in complex. The rate of hydrolysis of (NH 4) 2RuNOCl 5 was more rapid in basic solution than in acid solution by 25–50%. Values for these rate constants at 55′ are k acid = 5.20×10 −5 sec −1, ΔH * = 29.2 kcal/mole, ΔS * = 10.6 e.u.; k base = 7.13×10 −5 sec −1, ΔH * = 27.5 kcal/mole, ΔS * = 6.2 e.u. The rate of hydrolysis of (NH 4) 2RuNOCl 4OH proceeded at a rate independent of the hydrogen ion concentration below pH = 2.5 and in the range 7.5<pH<9.5. The acid base limiting rates differ by approximately 800. Values of the rate constants at 55′ and the activation parameters are: k acid = 8.90×10 −6 sec −1, ΔH * = 26.0 kcal/mole, ΔS * = −2.5 e.u.: k base = 7.14×10 −3 sec −1, ΔH * = 24.4 kcal/mole, ΔS * = 5.7 e.u. In addition the equilibrium quotient for the reaction RuNOCl 3(H 2O) 2+Cl −→RuNOCl 4H 2O − has been evaluated and the rate of anation of the trichloro complex evaluated.