How to tame a palladium terminal oxo

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Catalysis

Background:

• Terminal oxo complexes of late transition metals are crucial for oxidation catalysis but are difficult to isolate.
• While common for early transition metals, well-characterized examples with group 10 metals like palladium are rare.
• Understanding the electronic properties of ligands is key to stabilizing these reactive intermediates.

Purpose of the Study:

• To computationally evaluate the stability and reactivity of palladium terminal oxo complexes.
• To identify crucial electronic properties of ancillary ligands for stabilizing these complexes.
• To explore the potential of these complexes in oxidation catalysis, including C-H hydroxylation and water activation.

Main Methods:

• Utilized computational methods, including CASSCF/NEVPT2 and Density Functional Theory (DFT).
• Investigated well-established ligand systems relevant to coordination chemistry and homogeneous catalysis.
• Analyzed the electronic properties of ligands and their impact on palladium oxo complex stability.

Main Results:

• Identified carbene ligands with strong σ-donor and π-acceptor properties as optimal for stabilizing palladium(II) terminal oxo complexes.
• Determined that weaker ligand fields result in highly reactive complexes.
• Found that strongly donating ligands are suitable for high-valent palladium(IV) terminal oxo compounds.
• Concluded that low-coordinate palladium(II) and high-valent palladium(IV) complexes are promising for strong bond activation.

Conclusions:

• Specific ligand electronic properties, particularly those of carbene ligands, are critical for stabilizing reactive palladium terminal oxo complexes.
• These stabilized complexes offer potential for advancing oxidation catalysis, including selective C-H functionalization and strong bond activation.
• Computational evaluation provides a pathway to designing effective catalysts for challenging chemical transformations.