Oxygen atom transfer from a trans-dioxoruthenium(VI) complex to nitric oxide

Area of Science:

• Coordination Chemistry
• Inorganic Reaction Mechanisms
• Ruthenium Chemistry

Background:

• Ruthenium complexes, particularly high-valent species, are involved in various redox reactions.
• Nitric oxide (NO) is a versatile small molecule participating in biological and chemical processes.
• Understanding the reactivity of ruthenium-nitric oxide systems is crucial for catalysis and bioinorganic chemistry.

Purpose of the Study:

• To investigate the reaction kinetics and mechanism between a specific ruthenium(VI) complex and nitric oxide (NO).
• To identify intermediate species and elucidate the electron transfer pathways.
• To compare the reaction mechanism in aqueous and acetonitrile solutions.

Main Methods:

• Spectrophotometric monitoring of reaction progress.
• Kinetic studies under varying concentrations of reactants.
• Thermodynamic analysis (activation enthalpy and entropy) in different solvents.

Main Results:

• The reaction of trans-[Ru(VI)(L)(O)(2)](2+) with excess NO yields trans-[Ru(L)(NO)(OH)](2+), with a second-order rate constant of (4.13±0.21)×10(1) M(-1) s(-1) at 298.0 K.
• A ruthenium(IV) intermediate, trans-[Ru(IV)(L)(O)(OH(2))](2+), was detected when less than one equivalent of NO was used.
• Similar thermodynamic parameters (ΔH≠ and ΔS≠) in water and acetonitrile suggest a conserved reaction mechanism, involving oxygen atom transfer to NO.

Conclusions:

• A mechanism involving oxygen atom transfer from the ruthenium(VI) complex to NO, forming NO(2), is proposed.
• The reaction of the ruthenium(IV) intermediate with NO proceeds via one-electron transfer, forming a nitrito species.
• The observed kinetics and thermodynamic data support a consistent reaction pathway across different solvent systems.