The kinetics and thermodynamics of a novel efficient mixed water–1,4‐dioxan solvent for the effective complexation of a neutral ruthenium complex with carbon monoxide at atmospheric pressure

Kinetic and thermodynamic investigations were performed for a mixed aqueous‐organic, 1:1 (v/v) water–1,4‐dioxane medium, which was found to be an efficient solvent for the interaction of a neutral dichlorotris(triphenylphosphine) ruthenium(II), RuCl 2 (PPh 3 ) 3 complex with carbon monoxide at atmospheric pressure. During the interaction, RuCl 2 (PPh 3 ) 3 dissociates to a neutral complex dichlorobis(triphenylphosphine) ruthenium(II), RuCl 2 (PPh 3 ) 2 , by losing a coordinated PPh 3 ligand and RuCl 2 (PPh 3 ) 2 coordinates with CO to form an in situ carbonyl complex RuCl 2 (CO)(PPh 3 ) 2 . The in situ formed carbonyl complex RuCl 2 (CO)(PPh 3 ) 2 was thoroughly characterized by equilibrium, spectrophotometric, IR, and electrochemical techniques. Under equilibrium conditions, the rate and dissociation constants for the dissociation of PPh 3 from RuCl 2 (PPh 3 ) 3 were found to be favorable for the formation of the carbonyl complex RuCl 2 (CO)(PPh 3 ) 2 . The rates of complexation for the formation of RuCl 2 (CO)(PPh 3 ) 2 were found to follow an overall second‐order kinetics being first order in terms of the concentrations of both carbon monoxide and RuCl 2 (PPh 3 ) 2 . The determined activation parameters corresponding to the rate constant (ΔH # = 35.9 ± 2.5 kJ mol −1 and ΔS # = −122 ± 6 J K −1 mol −1 ) and thermodynamic parameters corresponding to the formation constant (ΔH° = −33.5 ± 4.5 kJ mol −1 , ΔS° = −25 ± 8 J K −1 mol −1 , and ΔG° = −25.7 ± 2.0 kJ mol −1 ) were found to be highly favorable for the formation of the complex RuCl2(CO)(PPh3)2. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 359–369, 2008