Palladium Complexes Based on Tridentate Pyrazolyl-Ligands: Synthesis, Structures and Use in Suzuki Cross-Coupling Reactions

Abstract The reaction of [PdCl(Me)(cod)] (cod = 1,5-cyclooctadiene) with tridentate bis(pyrazolyl) ligands affords the alkyl-palladium(II) complexes [Pd(CH 3 )(NZN)][BF 4 ] ( 1 , NZN = 1,1′-(2,2′-oxybis(ethane-2,1-diyl)bis(3,5-dimethyl-1H-pyrazole); 2 , NZN = bis[2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]sulfane) in good yield. Compounds 1 – 2 were characterized by elemental analysis, multinuclear NMR spectroscopy, and X-ray structural analysis. Single crystal X-ray structural analyses indicate that the complexes are monomeric and the palladium center resides in a slightly distorted square planar environment. Furthermore, despite their intrinsic similarity, the NON and NSN ligands adopt different coordination modes around the palladium metal center. Additionally, the [PdCl 2 (NON)] ( 3 ) was shown to be an efficient catalyst precursor for the coupling of aryl bromides and iodides with arylboronic acids, esters and borate salts.