The Synthesis of [Pd(NHC)(acac)Cl]·(HFIP) Adducts and Their Catalytic Activity in the α‐Arylation of Ketones

We report the synthesis and catalytic evaluation of hydrogen‐bond‐stabilized palladium–N‐heterocyclic carbene (NHC) fluoroalkoxide adducts of the type [Pd(NHC)(acac)Cl]·(HFIP), (HFIP = 1,1,1,3,3,3‐hexafluoroisopropanol). These air‐stable complexes were readily obtained under ambient conditions and fully characterized, including by single‐crystal X‐ray diffraction analysis. Their catalytic performance was investigated in the α‐arylation of ketones. The HFIP‐stabilized adducts displayed significantly enhanced catalytic activity compared with the corresponding non‐HFIP containing analogs. Mechanistic investigations indicated that this effect originates from an alternative activation pathway that leads to the formation of the catalytically active [(NHC)Pd(0)] species. Furthermore, extensive optimization studies demonstrated that catalyst loadings as low as 1 ppm are sufficient to achieve high conversions under mild reaction conditions.