Palladium Schiff Base Complex Research Articles

Catalytic activity of the two magnetic nanoparticles-supported palladium catalysts for Suzuki coupling reaction under green conditions

Two palladium Schiff base complexes supported on magnetic nanoparticles, namely, P,N-Pd-Fe3O4 and CPS-MNPs-NNN-Pd, were successfully used as efficient heterogeneous catalysts for the Suzuki coupling reaction under mild and green conditions. We compared the catalytic activity of these two catalysts and the results indicated that the CPS-MNPs-NNN-Pd catalyst promoted the reaction more efficiently due to its structure. Only 0.1 mol% of CPS-MNPs-NNN-Pd catalyst was required to promote the Suzuki reactions and these reactions were performed efficiently for aryl iodides, bromides, and also chlorides. Notably, this catalyst had higher TON and TOF numbers than most of the previously reported catalysts. Moreover, the catalyst could be easily separated from the reaction mixture under the outer or external magnetic field and reused at least for 4 times without appreciable loss of its catalytic activity.

High Catalytic Activity, Recyclable and Magnetically Separable Nanocatalyst Fe3O4@SiO2-Schiff base-Pd(II) for Synthesis of 12H-Benzo[5,6]Chromeno[2,3-b]Pyridine-10-Carbonitriles and Evaluation of Antibacterial Activity

In this work, an effective and selective heterogeneous catalyst was produced by immobilization of palladium Schiff base-complexes on ferrite magnetite nanoparticles (MNP). The catalysts Fe3O4@SiO2-Schiff base-Pd(II) were synthesized using Fe3O4@SiO2 core–shell nanoparticles and functionalized with 3-chloropropyltrimethoxysilane (CPTMS) as Fe3O4@SiO2@Cl. The Schiff base ligand was synthesized by reaction of 2-hydroxy-1-naphthaldehyde with 4-aminophenol to produce of 1-(((4-hydroxyphenyl)imino)methyl)naphthalen-2-ol, then palladium acetate was added to produce of Schiff-base-Pd(II) complex. Finally, Fe3O4@SiO2-Schiff base-Pd(II) was synthesized by the reaction of Fe3O4@SiO2@Cl core–shell nanoparticles with Schiff-base-Pd(II). The catalyst was characterized by several techniques, such as FT-IR, TEM, EDX, XRD, TGA and VSM. An efficient tandem reaction approach is described to prepare novel 12H-benzo[5,6]chromeno[2,3-b]pyridine-10-carbonitrileusing 1 mol% catalyst in methanol. The described one-pot three-component reaction is characterized by short reaction time, high product yield, mild reaction conditions, simple workup procedure, simple purification and catalyst can be easily recovered and reused in at least seven sequential cycles without considerable leaching and loss of reactivity

Pd(II) Schiff base complex anchored on MCM-41, a reusable catalyst for the Heck reaction

A Palladium (II) Schiff base complex was implanted on the surface of MCM-41 to fabricate a simple and reusable catalyst using post-grafting methodology. The surface of MCM-41 initially modified with 3-chloropropyltriethoxysilane (CPTES), followed by the Schiff base ligand (PAL) and on reacting with PdCl2 results in the formation of MCM@CP@PAL@Pd complex. Characterization of the designed heterogeneous catalyst by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Microwave Plasma Atomic Emission Spectroscopy (MP-AES) and Brunauer–Emmett–Teller (BET) techniques indicated successful grafting of Palladium (II) complex inside the hexagonal channels of MCM-41.The MCM@CP@PAL@Pd catalyst was used for a good range of Heck reactions using different aryl halides with styrene or alkyl acrylate esters. The catalyst has low metal content, provides magnificent yield (95%) in a short time period (20 min), displayed excellent structural and chemical stability and can be reused seven times without remarkable change in its catalytic efficiency.

A palladium Schiff base complex covalently bonded to functionalized mesoporous MCM-41: a novel, green and highly efficient catalyst for Heck–Mizoroki and Suzuki–Miyaura cross-coupling reactions in water-medium

A palladium Schiff base complex covalently bonded to functionalized mesoporous MCM-41: a novel, green and highly efficient catalyst for Heck–Mizoroki and Suzuki–Miyaura cross-coupling reactions in water-medium

Spectroscopic investigation, molecular structure, catalytic activity with computational studies of a novel Pd(II) complex incorporating unsymmetrical tetradentate Schiff base ligand

The treatment of an unsymmetrical tetradentate Schiff base ligand with Pd(OAc)2 salt yields novel palladium(II) Schiff base complex. The generated palladium(II) complex was characterized using elemental analysis (CHN) and different spectroscopic methods such as FT-IR and 1H NMR. Single crystal X-ray diffraction (SC-XRD) investigation has also been used to examine the crystal structure of the palladium complex. It is revealed from the SC-XRD study that the palladium ion in the complex is tetra-coordinated, inhabited by ONNO donor sites of the chelated ligand in a distorted square planar manner. The non-covalent interactions were explored by Hirshfeld surface analysis. The theoretical parameters calculated by DFT using the B3LYP/Def2-TZVP level of theory revealed that the theoretical conclusions matched the actual findings. For different aryl halides, the palladium(II) complex has exhibited excellent efficiency in the Suzuki-Miyaura cross-coupling reactions (SMCR), yielding biaryls in good to high yield.

Comparative study of palladium(II) complexes bearing tridentate ONS and NNS Schiff base ligands: Synthesis, characterization, DFT calculation, DNA binding, bioactivities, catalytic activity, and molecular docking

Two palladium (II) Schiff base complexes were prepared by using equivalent molar of Schiff base ligand [L1= (E)-2-(((2-(benzylthio)phenyl)imino)methyl)naphthalen-1-ol and L2= (E)-N-(2-(benzylthio)phenyl)-1-phenyl-1-(pyridin-2-yl)methanimine] and sodium tetrachloropalladate. The structure of ligands and complexes were characterized by physicochemical and spectroscopic analyses. The results suggested that the Pd(II) complexes have a distorted square planar geometry when coordinated to the tridentate ONS from L1 and the NNS donor ligand from L2. Electronic absorption and spectrofluorometric measurements were employed to investigate the DNA binding of ligands and their associated complexes with CT-DNA. DFT calculations were used to optimize the geometric structures and calculate the electronic and structural properties of the synthesized compounds. NBO analysis was also performed in combination with the TD-DFT method. Moreover, to study the reactivity and bioactivity, the synthesized compounds were tested for in-vitro antioxidant activity by utilizing the DPPH method, in-vitro anti-inflammatory activity using protein denaturation method, and in-vitro anti-diabetic activity employing α-glucosidase and α-amylase enzymes. The results reflect that PdL1 is more biologically potent than PdL2 or other related palladium complexes, as discussed in the literature. The binding mechanism of the synthesized compounds with CT-DNA, α-glucosidase, and α-amylase, was investigated using molecular docking experiments. In addition to these, the catalytic activity of palladium metal complexes (PdL1 and PdL2) was evaluated for the Suzuki-Miyaura reaction for comparisons.

Palladium(II) Schiff base complex arrests cell cycle at early stages, induces apoptosis, and reduces Ehrlich solid tumor burden: a new candidate for tumor therapy.

Although many cancer drugs are clinically approved, they still suffer from no adequate efficiency or drug resistance, or bad side effects. Therefore, developing safer alternatives of competitive efficiency is needed. This study aimed to investigate, for the first time, the antitumor and apoptotic activities of palladium(II) 2-hydroxyimino-3-(2-hydrazonopyridyl)-butane complex against Ehrlich carcinoma. In vitro, EAC cells were incubated with the complex, and the cells' viability, caspase 8 activity, and cell cycle changes were evaluated. In vivo, eighty adult female Swiss albino mice were distributed randomly in the following groups (n = 10): Normal, EAC, EAC + Cisplatin, and four groups EAC + Complex as well as Normal + Complex. Bodyweight changes were noted. On day 22 mice were sacrificed. Tumors' volume and weight were recorded. Blood picture was routinely investigated. The median survival time (MST) and percent increase in life span (%ILS) were monitored. In vitro, the complex reduced the %viable EAC cells, increased caspase 8 activity, arrested cell cycle at G0/G1, and reduced G2(M) population indicating antiproliferative and antitumor activities via inducing apoptosis. Treatment with the complex in a dose-dependent mode significantly decreased tumor volume and weight, extended the MST and the %ILS, increased mice body weight gain, and improved the blood indexes. Treatment of EAC-bearing mice with the complex highest dose showed more desirable outcomes than treatment with cisplatin. The Normal + Complex group showed no pathological changes indicating safety. In conclusion, our outcomes recommend the Pd(II) complex as a new optimistic candidate for tumor therapy after further studies for validation.

Synthesis, Structural Characterization and Catalytic Activities of Palladium(II) Schiff base Complexes Containing Tetradentate N2O2 & N2S2 Donor Ligands

New family of palladium(II) tetradentate complexes of the general formula [Pd(L1-4)] (L1-L3; tetradentate N2O2 donors & L4; tetradentate N2S2 donors) have been synthesized by the reaction of Pd(OAc)2 with tetradentate Schiff base ligands. The palladium(II) complexes were fully characterized by analytical, spectral (FT-IR, UV-Vis, 1H-NMR & 13C-NMR) methods. Further, the new palladium(II) complexes were tested as catalyst for Suzuki-Miyaura and Sonogashira coupling reactions and exhibits very good catalytic activity.

Copper (II) and Palladium (II) Schiff‐Base Complexes as Homogeneous and Heterogeneous Catalyst for Efficient α‐Methyl Oxidation Reaction: Experimental and DFT Approaches

AbstractNew homogenous catalysts of Schiff base/M(II), (M(II)=Cu, Pd), and new heterogeneous catalysts [graphene oxide (GO)/3‐chlorotrimethoxisilane (CPS) /Schiff base/M(II)] has been successfully synthesized. The heterogenous catalysts were synthesized using 3‐chlorotrimethoxisilane (CPS) via covalent bonding on graphene oxide and were characterized using fourier transform infrared spectroscopy (FTIR), x‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x‐ray spectroscopy(EDS) techniques. Schiff base/M(II) and GO/CPS/Schiff base/M(II) were used as homogenous and heterogeneous catalysts in the oxidation of alkens. Catalytic results showed all the prepared samples were active in the oxidation of α‐methyl styrene. Over as‐prepared heterogeneous catalysts, more than 99 % conversion and selectivity for acetophenone could be achieved using (tert‐butyl hydroproxide (TBHP) : 22.5 mmol, Acetonitrile as solvent after 6 h).The recyclability experiment results indicated that heterogenous catalysts are excellent for α‐methyl styrene conversion and acetophenone selectivity even after being used for four cycles. Moreover, the electronic structures and net atomic charges are interpreted by density functional theory (DFT) calculations. Running title: Copper (II) and palladium (II) Schiff base complexes for experimental and theory study

High volume hydrogen evolution from KBH4 hydrolysis with palladium complex catalyst

Abstract In this work, we aimed to present an efficient catalyst in potassium borohydride hydrolysis for hydrogen production. Therefore 5-Amino-2,4-dichlorophenol-3,5-ditertbutylsalisylaldimine-Pd complex was synthesized. FT-IR, SEM, TEM, BET, XRD, Elemental Analysis techniques was employed for characterization of Pd-complex catalyst. When the catalyst tested in KBH4 hydrolysis reaction, some affecting factors were studied such as temperatures (20°C-50 °C), catalyst amounts (5–50 mg), KOH concentrations (0–10%) and KBH4 concentration (2–10%) The results displayed that the synthesized Palladium Schiff Base complex catalyst facilitates potassium borohydride hydrolysis with 25.194 kJ/mol activation energy (Ea). Additionally, Pd Schiff Base complex demonstrated remarkable reusability performance and conserved 95% of its inherent catalytic activity even at sixth recycle.

Palladium(II) complexes comprising naphthylamine and biphenylamine based Schiff base ligands: Synthesis, structure and catalytic activity in Suzuki coupling reactions

New palladium(II) Schiff base complexes of the general formula [Pd(L1−6)2] [L1 = N-(Naphthyl)-salicylaldimine (1), L2 = N-(Naphthyl)-methoxysalicylaldimine (2), L3 = N-(Biphenyl)-salicylaldimine (3), L4 = N-(Biphenyl)-methoxysalicylaldimine (4), L5 = N-(Naphthyl)-2-hydroxy-1-naphthaldimine (5), L6 = N-(Biphenyl)-2-hydroxy-1-naphthaldimine (6)] 1–6 have been synthesized by the reaction of [Pd(OAc)2] with bidentate Schiff base ligands. The palladium(II) complexes were fully characterized by analytical, spectral (FT−IR, UV–Vis, 1H NMR &13C NMR) methods. The molecular structure of the one of the complexes [Pd(L1)2] (6) was confirmed by single crystal X−ray diffraction methods. Further, the new palladium(II) complexes were tested as catalyst for Suzuki-Miyaura coupling reactions and exhibits very good catalytic activity.

Palladium schiff base complex immobilized on magnetic nanoparticles: An efficient and recyclable catalyst for Mizoroki and Matsuda-Heck coupling

The present work elucidates the catalytic efficiency of palladium Schiff base complex immobilized on amine functionalized magnetic nanoparticles for Heck coupling of structurally different aryl halide/arenediazonium tetrafluoroborate with styrene/acrylate/acrylonitrile. Matsuda-Heck coupling proceeds in aqueous media at room temperature whereas Mizoroki-Heck coupling was carried out at 80 °C. Both reactions were successfully furnished with low catalyst loading. The catalyst was easily separated from reaction mixture and reused up to six times without significant loss of catalytic activity.

Synthesis and Characterization of New Palladium(II) Schiff Base Complexes Derived from β-Diketones and Diamines

A new series of heterocyclic Schiff bases were prepared from condensation of 1-phenyl-3-methyl-4-acetyl/benzoyl-pyrazolone with 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenyl ether, resulting in the formation of four novel Schiff base ligands. These ligands were then treated with ethanolic solution of PdCl2, to form corresponding palladium(II) complexes. These complexes were characterized by elemental analysis, IR, 1H NMR, TGA, magnetic susceptibility measurements and UV-visible absorption spectroscopy. All the Pd(II) complexes were found to have one coordinated water molecule. Schiff base ligands chelated with the metal atom through two donor sites N and O of azomethine (-C=N-) and phenolic (-OH) groups, respectively.

Crystal structure and evaluating C[sbnd]H⋯π (aryl/chelate) interactions in bis(2-{[(2-hydroxyethyl)imino]-methyl}-4,6-diiodophenolato)-palladium(II) Schiff base complex derived from (E)-2-(((2-hydroxyethyl)imino)methyl)-4,6-diiodophenol

A novel PdII complex [bis(2-{[(2-hydroxyethyl)imino]methyl}-4,6-diiodophenolato)-Palladium(II), (Pd(L1))] has been synthesized using a N,O-donor Schiff base ligand, (E)-2-(((2-hydroxyethyl)imino)methyl)-4,6-diiodophenol (L1). The structure of Pd(L1) has been confirmed by single crystal X-ray diffraction analysis. Pd(L1) shows unusual CH⋯π (chelate) interaction beside with the usual CH⋯π (aryl) interactions in the solid-state. A comprehensive analysis of Hirshfeld surfaces and fingerprint plots are useful to measure the interactions within the crystal structure. The CH⋯π (chelate/aryl) interactions and the binding energies of noncovalent interactions observed in the crystal structure were analyzed using theoretical DFT calculations. Besides, the interactions have been exemplified by using both Bader’s theory of AIM analysis and the noncovalent interaction plot. The topological analysis of the electron density was carried out to analyze the bonding nature in the complex.

Magnetic Mesoporous Silica Nanocomposite Functionalized with Palladium Schiff Base Complex: Synthesis, Characterization, Catalytic Efficacy in the Suzuki–Miyaura Reaction and α-Amylase Immobilization

Magnetic mesoporous silica nanocomposite, Fe3O4-MCM-41, was functionalized with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS) and then condensed with 5,5′-methylene bis(salicylaldehyde), followed by N(4)-phenylthiosemicarbazide to produce a ONS Schiff base grafted nanocomposite. Finally, by adding palladium(II) acetate, the palladium Schiff base complex was immobilized on magnetic nanocomposite. The characterization of new nanocomposites was carried out by means of several techniques such as FT-IR, XRD, FE-SEM, HRTEM, EDS, BET, VSM, XPS, DRS and TGA. The new nanocatalyst, Fe3O4@MCM-41-SB-Pd, was used in synthesis of symmetrical and unsymmetrical biaryl compounds via the Suzuki–Miyaura cross-coupling of phenylboronic acid with aryl halides. This catalyst was easily recovered by applying an external magnetic field and reused for several times without significant loss of its catalytic activity. Also the ability of synthesized mesoporous nanocomposites for enzyme immobilization was investigated and results showed that they efficiently immobilized α-amylase enzyme.

Encapsulation of a Palladium Schiff‐Base Complex into the Nanocages of Mesoporous SBA‐16 as an Efficient Heterogeneous Catalyst for the Suzuki‐Miyaura Coupling Reaction in Water

AbstractA palladium Schiff base complex was successfully encapsulated in the nanocages of SBA‐16 by post‐reducing the pore entrance size through a simple silylation method. The prepared material was demonstrated to be a high‐performance and efficient heterogeneous catalyst in the Suzuki‐Miyaura reaction of a wide range of aryl halides with arylboronic acids even with low palladium loading (0.01 mol%) under mild aqueous condition. The catalyst could be recovered by simple filtration from the reaction mixture and reused for eight cycles with no change in catalytic performance confirming its good stability. Comparison of the activity of free and encapsulated complex revealed that placement of the complex in the nanocages of SBA‐16 did not compromise its catalytic activity. Moreover, based on the experimental results, we proposed a possible reaction mechanism, which was further confirmed by density functional theory (DFT) calculations.

Palladium-Schiff Base Complexes Encapsulated in Zeolite-Y Host: Functionality Controlled by the Structure of a Guest Complex.

A series of palladium complexes of tetradendate Schiff base ligands L1 ( N,N'-bis(salicylidene)phenylene-1,3-diamine) and its derivatives L2 and L3 have been synthesized by using the "flexible ligand method" within the supercage of zeolite-Y. These complexes in both their free and encapsulated states have been thoroughly characterized with the help of different characterization tools such as XRD, SEM-EDS, BET, thermal analysis, XPS, IR, and UV-vis spectroscopic studies. All these encapsulated complexes are identified with a dramatic red shift of the d-d transition in their electronic spectra when compared with their free states. Theoretical as well as experimental studies together suggest a substantial modification of the structural parameters of square planar Pd(II)-Schiff base complexes upon encapsulation within the supercage of zeolite-Y. Encapsulated complexes are also subject to show modified catalytic activities toward the Heck reaction. These heterogeneous catalysts can easily be separated from the reaction mixture and reused.

Dinuclear Pd(II) complexes containing bis-O,N-bidentate Schiff base ligands: Synthesis, characterization, DFT study and application as Suzuki–Miyaura coupling catalysts

The reaction of binucleating Schiff base ligands with [PdCl2(PPh3)2] and [Pd(OAc)2] afforded a new family of binuclear palladium(II) Schiff base complexes of the type [Pd2(L)2] and [Pd2Cl2(PPh3)2(L)]. All the palladium complexes are air stable and fully characterized by elemental analysis, FT-IR, UV–Vis and 1H NMR spectral methods. These palladium(II) Schiff base complexes exhibit characteristic metal to ligand charge transfer (MLCT) transitions. Quantum mechanical calculations were also performed to investigate the electronic structure, assign the vibrational spectra and to determine the nature of the frontier molecular orbitals and absorption spectra of the above complexes. These palladium(II) Schiff base complexes exhibited good catalytic activity in the carbon–carbon Suzuki coupling reaction of different aryl halides using phenyl boronic acid.

Unsymmetrical palladium(II) N,N,O,O-Schiff base complexes: Efficient catalysts for Suzuki coupling reactions

Abstract Palladium offers various applications in the field of fine chemicals. As one of the most widely used catalytic metals, due to its high activity and selectivity, there are many possibilities for carbon-carbon bond formation in the organic synthesis. This study focused on the condensation reaction between the selected aldehyde or ketone, and 1, 2-Phenylenediamine; as a result, two different Schiff base ligands were prepared. The reaction between palladium(II) acetate and Schiff base ligand, in a molar ratio of 1:1, resulted in the formation of palladium(II) Schiff base complexes PdL 1 and PdL 2 ( L 1 = N-2-hydroxyacetophenon-N′-2, 4-dihydroxbenzaldehyde-1,2 phenylenediimine, and L 2 = N-2-hydroxyacetophenon-N′-2-hydroxynaphthaldehyde-1,2 phenylenediimine), as identified by elemental analysis, FT-IR, UV–Vis and 1 H NMR spectroscopies. The X-ray analysis of PdL 2 also showed that the Schiff base acted as a tetradentate ligand which, through both phenolic O and azomethine N atoms, could be coordinated to the Pd atom with the square planar geometry. By using GC, the catalytic activity of the Pd(II) complexes for the Suzuki coupling reaction was studied. After 8 h of reaction time at 70 °C in ethanol, it was concluded that both Pd(II) complexes served as good catalysts for this reaction by more than 90% conversion of the starting materials to the biphenyl product.

Tuning of Catalytic Property Controlled by the Molecular Dimension of Palladium-Schiff Base Complexes Encapsulated in Zeolite Y.

Planar palladium–Schiff base complexes are synthesized, maintaining the order of their molecular dimensions as PdL1 < PdL2 < PdL3 < PdL4 < PdL5 in free state, as well as encapsulated in zeolite Y, where L1: N,N′-bis(salicylidene)ethylenediamine and L2, L3, L4, and L5 are derivatives of L1. All encapsulated complexes have shown better catalytic activity for the sulfoxidation of methyl phenyl sulfide in comparison to their homogeneous counter parts. These hybrid systems are characterized with the help of different characterization techniques such as X-ray diffraction analysis, scanning electron microscopy–energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, Fourier transform infrared, and UV–visible spectroscopy; all of these studies have suggested that the largest complex deviates by the maximum from its free-state properties, and a radical change in the reactivity of the complex is observed.