Two‐Coordinate 13‐Electron Pd I Complexes Stabilized by the Bulky DIMeIHept Cl NHC Ligand

ABSTRACT Monomeric, two‐coordinate 13‐electron Pd I complexes are exceptionally rare due to their intrinsic instability and propensity for dimerization. In this study, we report that the bulky N‐heterocyclic carbene (NHC) ligand DiMeIHept Cl (1,3‐bis[2,6‐bis(1‐propylbutyl)phenyl]‐4,5‐dichloro‐1,3‐dihydro‐2 H ‐imidazol‐2‐ylidene) enables the generation and stabilization of a series of such species. Reduction of the dichloro Pd II precursor affords PdCl(DiMeIHept Cl ) ( 3 ), which serves as a platform for accessing Pd(OtBu)(DiMeIHept Cl ) ( 4 ), Pd[N(SiMe 3 ) 2 ](DiMeIHept Cl ) ( 5 ), and Pd(NH‐2,4,6‐tri‐tertbutyl‐C 6 H 2 )(DiMeIHept Cl ) ( 6 ). These complexes adopt pseudolinear or bent geometries, as established by EPR spectroscopy, x‐ray crystallography, and DFT calculations. Complexes 3 and 4 react with nucleophiles by an associative mechanism, which becomes impossible for sterically over‐crowded 5 . Kinetic and spectroscopic studies reveal divergent decay pathways, with 3 undergoing disproportionation and 4 – 6 decomposing via Pd─X bond homolysis to generate Pd 0 species and transient organic radicals. Notably, these Pd I complexes do not undergo oxidative addition with aryl halides, excluding Pd I/III reactivity under these conditions. Electronic structure analysis shows the unpaired electron resides primarily on Pd and the X ligand, with minimal NHC involvement. These findings provide insight into low‐coordinate Pd I intermediates that may prove relevant to Pd(NHC) precatalyst activation.