Reductively Stable Hydrogen-Bonding Ligands Featuring Appended CF₂-H Units

Area of Science:

• Organometallic Chemistry
• Supramolecular Chemistry
• Catalysis

Background:

• Hydrogen bonding is crucial in molecular recognition and catalysis.
• Unconventional hydrogen bond donors offer new possibilities for catalyst design.
• Metal complexes often utilize secondary coordination spheres to influence reactivity.

Purpose of the Study:

• To develop and characterize ligands featuring the -CF2H group as a hydrogen bond donor.
• To investigate the directed hydrogen bonding interactions in palladium complexes.
• To assess the utility of these ligands in metal-catalyzed reactions.

Main Methods:

• Synthesis of ortho-CF2H-functionalized 1,10-phenanthroline ligands.
• Metalation of ligands with palladium.
• Spectroscopic (e.g., NMR) and computational (e.g., DFT) analyses.
• Synthesis of Pd(0)/Ni(0) complexes and nickel-catalyzed coupling reactions.

Main Results:

• Demonstrated directed hydrogen bonding between the -CF2H group and Pd-coordinated substrates.
• Quantified the hydrogen bond strength (approx. 3 kcal/mol) with various acceptors.
• Synthesized stable Pd(0) and Ni(0) complexes.
• Showcased compatibility of the -CF2H donor with reductive and basic conditions during Ni-catalyzed coupling.

Conclusions:

• The -CF2H group acts as an effective and directed hydrogen bond donor in the secondary coordination sphere of palladium.
• These findings enable the design of novel catalysts with enhanced substrate interactions and broader reaction compatibility.
• This work expands the toolkit for supramolecular control in organometallic chemistry.