Neutral palladium(II) complexes with P,N Schiff-base ligands: Synthesis, characterization and application as Suzuki–Miyaura coupling catalysts

Palladium complexes containing NNN pincer type ligands and their activities in Suzuki-Miyaura cross coupling reaction

Five new NNN pincer-type ligands and their palladium complexes were successfully synthesised and characterised by FT-IR, ¹H NMR, ¹³C NMR, and UV-vis analyses. TEM analysis was used to observe the morphological character of the black residues obtained from the fourth cycle of the reusability test. Furthermore, suitable crystals of the N²,N⁶-bis(2-tert-butylphenyl)pyridine-2,6-dicarboxamide and its palladium complex were elucidated with the X-ray single crystal diffraction method. Both the ligand and its palladium complex crystallise in a monoclinic system with space group P2₁/c for the H₂L⁴ and C2/c for the palladium complex. The structure of the pincer ligand and its palladium complex were stabilised by intramolecular and intermolecular C-H⋅⋅⋅O, C-H⋅⋅⋅N, and N-H⋅⋅⋅N contacts. A Suzuki-Miyaura cross-coupling reaction between aryl halides and phenylboronic acid was used to assess the catalytic abilities of the palladium pincer complexes. All of the prepared complexes exhibited considerable catalytic activity. However, complexes 4 (Acetonitrile-N²,N⁶-bis(2-tert-butylphenyl)pyridine-2,6-dicarboxamidopalladium(II)) and 5 (Acetonitrile-N²,N⁶-bis(2-nitrophenyl)pyridine-2,6-dicarboxamidopalladium(II)) provided almost 100% conversion with nearly 100% yield in the reaction between 4-bromotoluene and phenylboronic acid. Furthermore, these active complexes catalysed the reaction of the sterically hindered and deactivated substrates (1-Bromo-4-izobutylbenzene and 2-bromo-6-methoxynaphthalene) with phenylboronic acid, and complete conversion and yields up to 100% were achieved in a short time with the 2-bromo-6-methoxynaphthalene.

Nickel complexes based on hyperbranched bispyridylamine ligands as catalyst precursors for ethylene oligomerization

A series of nickel complexes containing bispyridylamine ligands is synthesized and characterized by UV-Vis, FTIR, 1H NMR, ESI-MS, and elemental analysis. All nickel complexes activated with methylaluminoxane exhibited moderate activity for ethylene oligomerization (5.30 × 104 to 2.54 × 105 g/(mol·Ni·h)), producing oligomers in the range C4–C18. The effects of reaction temperature, reaction pressure, Al/Ni molar ratio, and solvent type on the catalytic activity and product selectivity are also investigated. The resulting products are mainly low-carbon olefins (C4 and C6). Under the optimized conditions, the complex with R1 = C4H9 formed by the reaction of the corresponding ligand R1 = C4H9 with NiCl2·6H2O showed a higher catalytic activity of 2.54 × 105 g/(mol·Ni·h) compared to the complex with R2 = C6H13 and R3 = C6H11 using toluene as the solvent. Moreover, the selectivity for the C4 and C6 oligomers can reach up to 82%.

Pd-Catalyzed, Highly Selective C(sp²)-Br Bond Coupling Reactions of o-(or m-, or p-) Chloromethyl Bromobenzene with Arylboronic Acids

Highly selective C(sp²)–C(sp²) cross-coupling of dihalogenated hydrocarbons comprising C(sp²)–Br and C(sp³)–Cl bonds with arylboronic acids is reported. This highly selective coupling reaction of the C(sp²)–Br bond is successfully achieved using Pd(OAc)₂ and PCy₃·HBF₄ as the palladium source and ligand, respectively. A series of chloromethyl-1,1′-biphenyl compounds are obtained in moderate-to-excellent yields. Moreover, this protocol can be extended to the one-pot dual arylation of 1-bromo-4-(chloromethyl)benzene with two arylboronic acids, leading to diverse unsymmetrical 4-benzyl-1,1′-biphenyl derivatives.

Assembly of silver-oxo complexes based on N-diphenylphosphanylmethyl-3-aminopyridine and their structures, photocatalysis and photocurrent responses

Compound {[Ag(μ-η²-Sal)(3-dppmapy)]}_n exhibits prompt anodic photocurrent responses and high photocatalytic performance in the degradation of organic dyes.

Synthesis and antioxidant activities of transition metal complexes based 3-hydroxysalicylaldehyde-S-methylthiosemicarbazone

The nickel(II), iron(III), oxovanadium(IV) complexes of the 3-hydroxysalicylidene-S-methyl-thiosemicarbazone (L) were obtained from the 3-hydroxysalicyldehyde-S-methylthiosemicarbazone with the R1-substituted-salicylaldehyde (R1: H, 3-OH) in the presence of Ni(II), Fe(III), VO(IV) as template ion. The ligand and its complexes were characterized by elemental analysis, electronic, UV/Vis., (1)HNMR, EPR and IR studies. The free ligand and its metal complexes have been tested for in vitro antioxidant capacity by reduction of copper(II) neocuproine (Cu(II)-Nc) using the CUPRAC method. The ligand exhibited more potent in vitro antioxidant capacity than its complexes. The obtained trolox equivalent antioxidant capacity (TEAC) value of the iron(III) complex (TEACCUPRAC=3.27) was higher than those of other complexes. Furthermore, the antioxidant activity of the free ligand and its complexes were determined by in vitro methods measuring the scavenging activity of reactive oxygen species (ROS) including hydroxyl radical (OH), superoxide anion radical (O2(-)), and hydrogen peroxide (H2O2), showing that especially the V(IV) and Fe(III) complexes had significant scavenging activity for ROS.

Palladium(ii) complexes containing ONO tridentate hydrazone for Suzuki–Miyaura coupling of aryl chlorides in aqueous-organic media

Robust and recyclable pincer type palladium(ii) complexes for Suzuki–Miyaura coupling of challenging aryl chlorides in aqueous-organic media.

Synthesis of Schiff Bases from Substitute Aromatic Aldehydes and 2-(4-aminophenyl)acetonitrile Catalysed by 3,5-difluoroarylboronic Acid

A simple efficient method for synthesis of Schiff bases in good yields from aromatic aldehydes and 2-(4-aminophenyl)acetonitrile catalysed by 3,5-difluoroarylboric acid at room temperature for 2 hours is reported.