Azo-amide palladium(II) complexes: Synthesis, characterization and application in C–C cross-coupling reactions. (15th October 2017)

• Record Type: Journal Article
• Authors: Pratihar, Jahar Lal; Mandal, Paritosh; Lin, Chia-Her; Lai, C.-K.; Mal, Dasarath
• Is Part Of: Polyhedron. Volume 135(2017)
• Page Start: 224
• Page End: 230
• Publication Date: 2017-10-15
• Subjects: Bis-2, 2′-(N-alkylamino)azobenzene -- Crystal structure -- Palladium(II) -- Catalysis -- Suzuki and Heck reaction; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2017.06.055
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: The newly designed tridentate ligands bis-2, 2′-( N -alkylamino)azobenzene and their corresponding palladium(II) complexes were synthesized and structurally characterized. The new palladium amido complexes were formed through beta proton elimination from the ligand precursor. One of the newly synthesized air and moisture stable palladium(II) amido complexes acts as a potential catalyst towards C–C bond formation for a variety of substrates under mild conditions. Abstract: The newly designed tridentate ligands bis-2, 2′-( N -alkylamino)azobenzene, 1a-1d, have been prepared by the reaction between 2, 2′-diaminoazobenzene and alkyl halides in the presence of K2 CO3 . These ligands were reacted with Na2 [PdCl4 ] in a 1:1 ratio in methanol to give the new Pd(II) complexes2a –2d . All the compounds were characterized by 1 H NMR, IR spectroscopy and elemental analysis. Furthermore, the solid-state structures of the ligand1a and two complexes (2a and2c ) were determined using single crystal X-ray diffraction analysis. The diffraction analysis revealed that the ligands bind with the Pd(II) ion in a monoanionic tridentate (N, N, N) fashion, offering a distorted square planar geometry where the fourth position is occupied by one chloride ligand. The air/moisture stable complex2a was employed as an efficient catalyst for the Suzuki and Heck reactions under mild conditions. The catalyst exhibits high catalytic activities for the coupling of several aryl halides with phenyl boronic acid and styrene, providing excellent yields. Further, the catalyst can be easily recovered by simple chromatographic separation and reused up to three times without significant loss of its catalytic activity.