Metal-Ion Influence on Ligand-Centered Hydrogen-Atom Transfer

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Chemical Kinetics

Background:

• Ligand-centered hydrogen-atom-transfer (HAT) is crucial in catalysis.
• Group 10 metal complexes with pincer ligands offer tunable reactivity.
• Understanding metal's influence on ligand HAT is key for catalyst design.

Purpose of the Study:

• To synthesize and characterize new palladium and platinum complexes with a [SNS] pincer ligand.
• To investigate the impact of the metal center (Ni, Pd, Pt) on ligand-centered HAT reactivity.
• To elucidate the thermodynamic and kinetic factors governing HAT in these complexes.

Main Methods:

• Synthesis of novel palladium and platinum [SNS] complexes.
• Thermodynamic measurements (bond dissociation free energies, pKa).
• Kinetic analyses of hydrogen-atom-transfer reactions.

Main Results:

• N-H bond dissociation free energies increase across the Ni < Pd < Pt series.
• This trend is driven by changes in ligand redox potential and pKa.
• Kinetic studies indicate entropic barriers dominate HAT reactivity.

Conclusions:

• The metal center plays a critical role in modulating ligand HAT reactivity.
• Thermodynamic stability increases from Ni to Pt, influencing reactivity.
• Entropic factors are the primary determinants of the HAT reaction barrier in this system.