Hydrogen Atom Abstraction via Hydride-Coupled Electron Transfer and Its Origin

Area of Science:

• Chemical Reaction Mechanisms
• Electron Transfer Processes
• Organometallic Chemistry

Background:

• Proton-coupled electron transfer (PCET) is a well-established reaction mechanism.
• Understanding alternative electron transfer pathways is crucial for catalysis and biochemistry.
• The role of hydride transfer in coupled electron transfer reactions requires further elucidation.

Purpose of the Study:

• To explore and define hydride-coupled electron transfer (HCET) as a distinct mechanism.
• To differentiate HCET from proton-coupled electron transfer (PCET) using experimental and theoretical evidence.
• To investigate the electronic and structural characteristics of HCET.

Main Methods:

• Computational analysis of reaction thermodynamics and kinetics.
• Electronic-structure calculations and descriptors.
• Intrinsic bond orbital analysis.

Main Results:

• HCET was identified in reactions involving Cu(III)-OH and Ni(II)-OH complexes.
• Thermodynamic cycles dictate whether HCET or PCET dominates.
• Electronic descriptors confirm hydride character in HCET and proton character in PCET.
• HCET involves a two-electron process with distinct electron migration pathways.

Conclusions:

• HCET is a fundamentally distinct mechanism from PCET.
• The mechanism is governed by favorable thermodynamic cycles.
• Detailed electronic structure analysis provides evidence for hydride transfer character.