[Pd(IPr*)(3-Cl-pyridinyl)Cl-2]: A Novel and Efficient PEPPSI Precatalyst

The preparation of the novel, well-defined [Pd(IPr*)(3-Cl-pyridinyl)Cl-2] complex is described. The steric parameters of the ligand as well as its reactivity in the Buchwald-Hartwig amination were directly compared to other [Pd(NHC)(3-Cl-pyridinyl)Cl-2] and [Pd(IPr*)(LX)Cl)] precatalysts (LX = cinnamyl or acac). The title complex exhibits similar catalytic activity to [Pd(NHC)(3-Cl-pyridinyl)Cl-2] congeners (NHC = IPr and SIPr) at room temperature. However, it also showed improved reactivity at low catalyst loading and high temperature (as low as 0.025 mol %). On the other hand, it proved to be as efficient as the previously reported [Pd(IPr*)(cinnamyl)Cl] complex, pointing to the most likely existence of a similar catalytically active species.