[Pd(NHC)(allyl)Cl] complexes: Synthesis and determination of the NHC percent buried volume (%Vbur) steric parameter

Complexes of palladium bearing NHC ligands (NHC=N-heterocyclic carbene) were synthesized and fully characterized. The [Pd(NHC)(allyl)Cl] series was obtained by simple cleavage of [Pd(allyl)Cl]₂ by using either the isolated free NHC or the in situ generated NHC. The NHC ligand sterics were varied by introduction of groups attached to the C4-C5 carbon atoms of the NHC backbone. Results of the X-ray diffraction study permitted determination of the NHC steric parameters within this series. It was observed that the NHC backbone induces variations in its percent buried volume (%Vbur) as a function of the N-substituents.