Room temperature olefination of methane with titanium-carbon multiple bonds

Area of Science:

• Organometallic Chemistry
• Homogeneous Catalysis
• C-H Activation

Background:

• Methane (CH4) is an abundant, underutilized C1 feedstock.
• Efficient catalytic methods for methane functionalization remain a significant challenge.
• Homogeneous systems for selective C-H activation and coupling are highly sought after.

Purpose of the Study:

• To develop a homogeneous catalytic system for methane C-H activation and dehydrocoupling at room temperature.
• To investigate the role of redox-active ligands in facilitating methane functionalization.
• To elucidate the mechanism of olefin formation via selective C-C bond formation.

Main Methods:

• Utilized a titanium alkylidene complex, (PNP)Ti[double bond, length as m-dash]CH(CH3)Bu (1).
• Employed redox-active ligands, thioxanthone and 2,2'-bipyridine (bipy), as exogenous additives.
• Combined computational studies and isotopic labeling experiments to probe the reaction mechanism.

Main Results:

• Achieved room temperature C-H activation of methane and subsequent dehydrocoupling.
• Formation of olefin H2C[double bond, length as m-dash]CHBu was observed via addition of ligands to complex 1.
• Redox-active ligands were shown to facilitate C-C bond formation by stabilizing a Ti(III) intermediate and trapping hydrogen atoms.

Conclusions:

• Demonstrated the first homogeneous models for room temperature methane activation and selective dehydrocoupling.
• Highlighted the dual role of redox-active ligands in promoting C-C coupling and stabilizing reactive intermediates.
• Established a new pathway for selective olefin synthesis from methane using organometallic catalysts.