Oxygen-promoted C-H bond activation at palladium

Area of Science:

• Organometallic Chemistry
• Catalysis
• Oxidation Reactions

Background:

• Palladium complexes are vital in catalysis.
• Aerobic oxidation of hydrocarbons is a key industrial process.
• Understanding reaction mechanisms is crucial for catalyst design.

Purpose of the Study:

• To investigate the reaction of a specific palladium complex with molecular oxygen.
• To elucidate the mechanism of C-H and O-O bond cleavage.
• To identify key intermediates in the aerobic oxidation pathway.

Main Methods:

• Reaction of [Pd(P(Ar)(tBu)2)2] with O2.
• Low-temperature spectroscopic observations.
• Computational studies to locate transition states.

Main Results:

• Formation of Pd(II) hydroxide dimers with cyclometalated naphthyl rings.
• Release of one phosphine equivalent per palladium.
• Evidence for superoxo and peroxo intermediates.
• Computationally identified transition state for C-H activation across a Pd-peroxo bond.

Conclusions:

• The reaction proceeds via initial superoxo and peroxo complexes.
• C-H activation occurs across a Pd-peroxo bond.
• This mechanism provides insights into catalytic aerobic oxidations.