Acetylacetonato-based pincer-type nickel(ii) complexes: synthesis and catalysis in cross-couplings of aryl chlorides with aryl Grignard reagents

Abstract

In this work, three different types of acetylacetonato-based pincer-type nickel(II) complexes (2) were prepared. Complex 2a possessed the tridentate ONN ligand, which was constructed by the condensation reaction of acetylacetone with N,N-diethylethylenediamine. Complex 2b contained the PPh₂ donor group in contrast to the NEt₂ group in 2a, i.e., an ONP ligand framework. Complex 2c was composed of the NNN ligand, which was prepared by the reaction of 4-((2,4,6-trimethylphenyl)amino)pent-3-en-2-one with N,N-diethylethylenediamine. In addition to X-ray diffraction analysis, these complexes were characterized spectroscopically. Their catalytic activity for a cross-coupling reaction of aryl halides with aryl Grignard reagents was also evaluated. Among these complexes, 2b acted as an effective catalyst for the cross-coupling reaction using aryl chlorides as electrophiles. The electronic properties of these Ni(II) complexes were investigated by cyclic voltammetry and density functional theory calculations.