A new air-stable Pd-PEPPSI N-heterocyclic carbene complex: Synthesis, structure, computational and catalytical studies

In this work, we have synthesized a new, air and moisture stable, Pd-PEPPSI (pyridine enhanced pre-catalyst preparation, stabilization and initiation) complex, [PdBr2(NHC)Py] (NHC is 3-benzyl-1-(4-methoxyphenyl)-1Himidazolline-2-ylidiene) and successfully employed as catalyst under mild conditions (35 degrees C, 0.5 mol% Pd loading) Suzuki-Miyaura cross-coupling reactions of aryl halides with aryl boronic acids in aqueous isopropanol. A wide range of aryl bromides / iodides were effectively utilized as coupling partners with arylboronic acids to afford corresponding biaryls in moderate-to-excellent yields. The complex was characterized by ESI-MS, 1H and 13C NMR spectroscopy and the molecular structure was determined by X-ray single crystal analysis. In order to gain more insight about structure, bonding and electronic properties, density functional theory (DFT) studies were performed. Moreover, TDDFT calculations were also performed to interpret the observed electronic absorption bands in the UV-VIS spectra. A good agreement between experimental and theoretical data was observed.