Synthesis, characterization, crystal structure and catalytic activity of amido azo palladium(II) complex
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Synthesis, characterization, crystal structure and catalytic activity of amido azo palladium(II) complex Jahar Lal Pratihar1 · Paritosh Mandal1 · Dasarath Mal2 · Chia‑Her Lin3 Received: 15 January 2020 / Accepted: 3 June 2020 © Springer Nature Switzerland AG 2020
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 K 2CO3. This ligand was reacted with N a2[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.
Introduction In the last three decades, palladium-catalyzed cross-coupling reactions leading to formation of C–C, C–N, C–O, and C–S bonds have become widely used in laboratory preparation, as well as industrial fine chemical synthesis [1–6]. Most of the works reported an efficient catalytic system for cross-coupling reactions based on the sterically demanding electron-rich phosphines, and its analogs [1, 2, 7–10]. However, palladium phosphines have several disadvantages, including toxicity, sensitivity to air and moisture, and difficult separation from the products [11–13]. To avoid this disadvantage several phosphine free systems have emerged Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11243-020-00407-7) contains supplementary material, which is available to authorized users. * Jahar Lal Pratihar [email protected] 1
Department of Chemistry, Kandi Raj College, Murshidabad 742137, India
2
Department of Chemistry, Vijaygarh Jyotish Ray College, Kolkata 700032, India
3
Department of Chemistry, National Taiwan Normal University, Ting‑Chow Rd., Taipei, Taiwan
as an alternative [14–20]. The unique steric and electronic properties of some ligands as well as their specific coordination mode and their strong binding ability to the formation of highly active and stable metal complexes which are more active catalyst for coupling reactions [21–23]. Still palladium phosphines are an important catalyst for crosscoupling reactions because phosphines control the catalytic cycle to maintain the
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