Synthesis, characterization, crystal structure and catalytic activity of amido azo palladium(II) complex

Abstract

The newly designed tridentate ligand, 2-((2-aminophenyl)diazenyl)-N-benzylaniline, 1 has been synthesized by the reaction between 2,2′-diaminoazobenzene and benzyl chloride in presence of K2CO3. This ligand was reacted with Na2[PdCl4] in methanol to give the new Pd(II) complex 2. Both the ligand and complex were characterized by usual spectroscopic techniques. Furthermore, the solid-state structure of complex 2 was determined using single crystal X-ray diffraction analysis. It revealed that the ligand binds with Pd(II) in dianionic tridentate (N,N,N) fashion offering distorted square planar geometry where fourth position is occupied by one phosphine ligand. The performance of the Pd(II) phosphine complex as catalyst was evaluated in the homogenous Suzuki and Heck reactions under mild conditions in presence of air and moisture. The Pd(II) complex showed good catalytic activities for the coupling of several aryl halides (iodides and bromides) with phenyl boronic acid and styrene providing excellent yields. After catalytic reactions, the catalyst has been recovered by simple chromatographic separation and reused for next reaction and its activity checked up to three cycles without sufficient loss. The newly designed tridentate ligand, 2-((2-aminophenyl)diazenyl)-N-benzylaniline and its corresponding palladium(II) complex were synthesized and structurally characterized. The neutral palladium(II) amido complex with phosphine as ancillary ligand was formed through two amino proton elimination from ligand precursor. The newly synthesized Palladium(II) complex acts as potential catalyst toward C–C bond formation for a variety of substrate under mild conditions in presence of air and moisture.