Vinyl C-F cleavage by Os(H)3Cl(P(i)Pr3)2

Area of Science:

• Organometallic Chemistry
• Catalysis
• Fluorinated Olefins

Background:

• Osmium complexes are known for their catalytic activity.
• Reactions involving fluorinated olefins present unique chemical challenges.
• Understanding reaction mechanisms is crucial for catalyst design.

Purpose of the Study:

• To investigate the reaction of Os(H)(3)ClL(2) with vinyl fluoride.
• To elucidate the reaction mechanism, including intermediates and catalytic pathways.
• To explore the role of hydrogen fluoride in C-F bond activation.

Main Methods:

• Variable-temperature Nuclear Magnetic Resonance (NMR) spectroscopy to identify reaction intermediates.
• Density Functional Theory (DFT) calculations (B3PW91) to determine potential and free energy landscapes.
• Competitive reaction studies and product analysis under varying conditions (e.g., HF scavenging).

Main Results:

• Identified key intermediates including OsHCl(H(2))(H(2)C=CHF)L(2), OsClF(=CHMe)L(2), and OsHCl(H(2))(C(2)H(4))L(2).
• DFT calculations highlighted the importance of entropy in intermediate stability.
• Demonstrated that hydrogen fluoride catalyzes C-F bond cleavage, with HF scavenging altering product distribution.

Conclusions:

• The reaction proceeds through multiple detected intermediates, with HF acting as a catalyst for C-F scission.
• High activation energy for unimolecular C-F cleavage suggests a catalytic pathway is essential for observed rates.
• The study provides mechanistic insights into the reactivity of osmium complexes with fluorinated alkenes.