[Pd(NHC)(allyl)Cl] Complexes: Synthesis and Determination of the NHC Percent Buried Volume (%V-bur) 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 (%V-bur) as a function of the N-substituents. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)