Structure and Reactivity of an Allylpalladium N-Heterocyclic Carbene Enolate Complex

A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the complex (NHC-enolate)Pd(allyl). At elevated temperatures in acetonitrile, the allyl ligand undergoes a stereoselective η 3 −η 1 −η 3 isomerization in an associative process that is first order in CD 3 CN with Δ H ⧧ = 13.5 ± 0.7 kcal mol - 1 and Δ S ⧧ = −17 ± 2 eu. This complex reacts with electrophiles (HCl, CH 3 I) at the enolate position.