Catalytic Dehydrogenative C-C Coupling by a Pincer-Ligated Iridium Complex

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Vinyl arenes are versatile building blocks in organic synthesis.
• Efficient catalytic methods for C-H functionalization are highly sought after.

Purpose of the Study:

• To investigate the catalytic activity of pincer-iridium complexes in the dehydrogenative coupling of vinyl arenes.
• To elucidate the reaction mechanism and explore substrate scope.

Main Methods:

• Catalysis using pincer-iridium fragments (iPrPCP)Ir.
• Density Functional Theory (DFT) calculations.
• Synthesis and characterization of metalloindene intermediates.
• Reactions with substituted styrenes.

Main Results:

• Predominant formation of (E,E)-1,4-diaryl-1,3-butadienes via dehydrogenative coupling.
• Yields up to 90% achieved through disproportionation or with sacrificial hydrogen acceptors.
• Mechanism involves double C-H addition to form an iridium(III) metalloindene intermediate.
• Demonstrated coupling of C(sp2)-H and C(sp3)-H bonds using 2,4,6-trimethylstyrene.

Conclusions:

• Pincer-iridium complexes are effective catalysts for vinyl arene dehydrogenative coupling.
• The reaction proceeds through a metalloindene intermediate.
• The catalytic system is versatile and can couple various C-H bonds.