Functionalization and Hydrogenation of Carbon Chains Derived from CO

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Carbon monoxide (CO) and hydrogen (H2) are fundamental C1 feedstocks.
• Transformations of CO and H2 into valuable organic molecules are crucial for chemical synthesis.
• Existing methods for combining H2 and CO often lack selectivity and control over product structure.

Purpose of the Study:

• To develop selective catalytic reactions that utilize H2 and CO with organic electrophiles.
• To achieve controlled synthesis of hydrogenated C3 and C4 carbon chains.
• To elucidate the mechanism of CO homologation and subsequent hydrogenation steps.

Main Methods:

• Utilized tungsten hexacarbonyl [W(CO)6] as a catalyst precursor.
• Employed an aluminum(I) reductant to mediate CO homologation.
• Investigated reaction kinetics, including primary kinetic isotope effects (KIEs).
• Performed density functional theory (DFT) calculations to analyze reaction intermediates.

Main Results:

• Demonstrated selective formation of hydrogenated C3 and C4 carbon chains from H2, CO, and electrophiles (aldehydes, ketones, isocyanides).
• Established a mechanism involving CO homologation followed by functionalization and hydrogenation.
• Identified a key metallocarbene intermediate and elucidated its hydrogenation pathway through kinetic and computational studies.
• Achieved complete control over carbon chain length and functionality of the products.

Conclusions:

• The developed catalytic system provides a novel and highly selective method for synthesizing defined carbon chains from H2 and CO.
• The mechanistic insights gained from kinetic and DFT studies offer a deeper understanding of CO homologation and hydrogenation processes.
• This work significantly expands the limited repertoire of catalytic systems capable of controlled H2/CO coupling for value-added product synthesis.