A 100,000-Fold Increase in C–H Bond Acidity Gives Palladium a Key Advantage in C(sp 3 )–H Activation Compared to Nickel
Year: 2025
Type: article
Abstract: Carbon-hydrogen bond activation is a pillar of synthetic chemistry. While it is generally accepted that Pd is more facile than Ni in C-H activation catalysis, there are no experimental platforms available to directly compare the magnitude of C-H bond weakening between Ni and Pd prior to bond scission. This work presents the first direct measurements of C( sp 3 )-H bond acidity (p K a ) and bond dissociation free energy (BDFE) for a species containing a ligated alkane-palladium interaction (R 2 CH 2 ---Pd), also known as an agostic interaction. Through standard-state equilibrium measurements and advanced computational modeling, we show that Pd acidifies C( sp 3 )-H bonds a 100,000 times more than Ni (5 p K a units), indicating that acidification is a key factor making Pd a privileged metal in C( sp 3 )-H functionalization reactions.Energy Decomposition Analysis (EDA) calculations show that this is primarily due to a greater electrophilicty of the palladium containing fragment, as forward charge transfer (ΔE CTf ) from the agostic methylene moiety into [Pd] is significantly increased. More broadly, these valuable findings help unravel fundamental performance differences between Earth-abundant and precious metals, potentially guiding future ligand design efforts for catalysis.
DOI: 10.1021/jacs.5c07649
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4414081972