Pd-PEPPSI: X-ray Structure, Spectroscopic Analyses, and Quantum Mechanical Studies

Pyridine enhanced precatalyst preparation stabilization and initiation (PEPPSI) complexes contain two halides, an unstable pyridine derivative and a bulky N-heterocyclic carbene (NHC) ligand. In this study, a new palladium-PEPPSI complex, dichloro[1-allyl-3-(2,3,5,6-tetramethylbenzyl)benzimidazole-2-ylidene]pyridine palladium(II), was synthesized and fully characterized by elemental analysis, X-ray crystallography, FT-IR, H-1, and C-13 NMR spectroscopy techniques. In addition, the molecular geometries, vibrational frequencies, and H-1 and C-13 NMR chemical shift values of the complex in the ground state have been calculated using the density functional theory (DFT) method with B3LLP/SDD. The frontier molecular orbitals analyses have been performed to explain the energetics and chemical reactivity of palladium-PEPPSI complex. Stability of the complex resulting from hyperconjugative interactions has been analyzed with natural bond orbital (NBO) analysis. The non-linear optical (NLO) properties have also been described calculating the polarizability and first order hyperpolarizability of the compound.