Autocatalytic cathodic dehalogenation triggered by dissociative electron transfer through a C-H···O hydrogen bond

Area of Science:

• Organometallic Chemistry
• Catalysis
• Electrochemistry

Background:

• Intramolecular electron transfer (ET) is crucial for many catalytic processes.
• Understanding noncovalent interactions is key to designing efficient catalysts.

Purpose of the Study:

• To elucidate the mechanism of radical autocatalytic chloroform degradation.
• To investigate the role of noncovalent interactions in facilitating ET.
• To compare the catalytic system to enzymatic mechanisms.

Main Methods:

• Voltammetry to observe the electrochemical process.
• Density Functional Theory (DFT) calculations to predict interactions and electronic structure.
• Spectroscopic analysis (ΔνC-H red-shift) to confirm hydrogen bonding.

Main Results:

• A combined C-H···Oalkoxide hydrogen bond and Cl···πpyrazolyl dispersive interaction facilitates rapid intramolecular ET.
• The process leads to a radical autocatalytic degradation of chloroform, observed as a sharp drop in voltammetry.
• DFT predicted a crucial close contact between the Mo(I) SOMO and the C-Cl LUMO, driven by strong hydrogen bonding.
• The reaction proceeds via alternating electron and proton transfers, with inhibition by alcohols and olefins.

Conclusions:

• The study demonstrates a novel electrocatalytic pathway for chloroform degradation.
• Noncovalent interactions play a significant role in stabilizing the transition state and accelerating ET.
• The observed proximity, stabilization, and inhibition effects are analogous to enzymatic catalysis, offering insights into biomimetic approaches.