Rhodium Complex Capable of Electron Storage Activated by Hydrogen Molecules: A Computational Study

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Physical Chemistry

Background:

• Two-electron reductions are crucial in catalysis.
• Understanding the mechanism of H2 activation by metal centers in aqueous solution is key for developing efficient catalysts.

Purpose of the Study:

• To elucidate the mechanistic factors governing the two-electron reduction of a rhodium (Rh) center by H2 in aqueous solution using density functional theory (DFT).
• To provide design principles for aqueous-phase complexes enabling two-electron reductions with water as the electron source.

Main Methods:

• Density functional theory (DFT) calculations were employed to study the reaction mechanism.
• Intrinsic bond orbital analysis was used to understand the electronic interactions and acidity of the Rh center.

Main Results:

• A mechanism involving oxidative cleavage of H2 to form a Rh-hydride complex, followed by heterolytic cleavage and proton abstraction was proposed.
• Rhodium (Rh) facilitates H2 activation through back-donation and acts as a Brønsted acid, enabling efficient proton transfer.
• Comparative calculations for group 9 elements showed Rh uniquely combines favorable hydride complex formation and low-valent complex generation, leading to superior reactivity.

Conclusions:

• Rhodium (Rh) complexes offer a unique combination of properties for efficient two-electron reduction in aqueous media.
• The findings provide insights for designing novel catalysts for water-based redox transformations.