Suzuki Cross-Coupling Reaction Catalyzed by the Palladium Complex Pd[N-MorphC(S)NP(O)(OiPr)2-O,S]2

Suzuki cross-coupling reaction between phenyl bromide and phenylboronic acid, catalyzed by the palladium complex Pd[N-MorphC(S)NP(O)(OiPr)₂-1,5-O,S)]₂ in acetonitrile, toluene, THF or DMF has been investigated. Bases employed for the reaction were Na₂CO₃, K₂CO₃ or Cs₂CO₃. Varying largely the experimental conditions we found that excellent yields of the product were obtained using toluene and K₂CO₃ at 100 °C at the catalyst amount of 0.02 mmol.     

Zn(Pro) 2-promoted CuI-catalyzed synthesis of diphenyl sulfide derivations in ionic liquid

We report a mild, palladium-free synthetic protocol for the cross-coupling reaction of aryl chlorides and thiols under the assistance of Zn complexes of proline and CuI, with K₂CO₃ as the base, performed at 110 °C in ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF ₄). This protocol is particularly noteworthy given its experimental simplicity, high generality, and the exceptional level of functional group tolerations and low cost of the catalyst system.     

Production of Monoacylglycerols from Fully Hydrogenated Palm Oil Catalyzed by Hydrotalcite Loaded with K2CO3

This study reports a new method of producing high-purity monoacylglycerols (MAGs) by glycerolysis of fully hydrogenated palm oil (FHPO) catalyzed by hydrotalcite loaded with K₂CO₃ (K₂CO₃/HT). The effects of reaction temperature, reaction time, catalyst (K₂CO₃/HT) loading, and mass ratio of FHPO to glycerol on glycerolysis were investigated. The selected conditions included a reaction temperature of 200°C, K₂CO₃/HT loading at 0.8 wt.% (FHPO mass), a 5:2 mass ratio of FHPO to glycerol, and a reaction time of 2 h. Under these selected conditions, the yield of MAGs in the acylglycerol phase reached 46.8 wt.%. A two-stage molecular distillation was introduced to purify MAGs, and the final MAG product was obtained with a purity of 96.6 wt.% and a recovery of 96.8%. Furthermore, the recycled K₂CO₃/HT was reactivated with restored catalytic efficiency through impregnation, carbonation, and recalcination.     

Pincer Type Ditertiary Aminomethylphosphine–Pd(II) Complexes Supported on Multi-Walled Carbon Nanotube: Catalytic Properties in Heck C–C Coupling Reactions

Pincer type aminomethylphosphine–Pd(II) complexes supported on multi-walled carbon nanotube (MWCNT) have been synthesized and characterized using X-Ray diffraction spectrometry, scanning electron microscopy, thermal analysis, energy dispersive X-Ray, Fourier transform infrared spectrometry, transmission electron microscopy (TEM) and ultraviolet–visible spectrometry techniques. The novel complexes were tried as catalysts in Heck C–C coupling reactions. The crystallite size and lattice strain of the MWCNT based compounds were calculated by the Scherrer’s equation. The optical parameters of the MWCNT based structures were analyzed and the band gap enhanced from 4.42 to 4.98 eV. Different solvents (toluene, 1,4-diooxane, DMF and NMP) and bases (Et₃N, Na₂CO₃, NaOAc and K₂CO₃) were tried at different temperatures (80, 100 and 110 °C) in the cross-coupling of bromobenzene with styrene. The optimum yield was found in the presence of K₂CO₃, 110 °C in 1,4-dioxane solvent system.     

Absorption of Carbon Dioxide into Ionic Liquid of 2-Hydroxy Ethylammonium Lactate

Abstract

Absorption of carbon dioxide into organic solvents such as DMA, NMP, DMSO, and DMF with the 2-hydroxy ethylammonium lactate (HEAL) ionic liquid was investigated using a batch stirred tank with a plane of gas-liquid interface in a range of 0–2.0 kmol/m³ of HEAL and 298–318 K at 101.3 kPa. The absorption of CO₂ was analyzed with the film model accompanied by the zwitterion mechanism of CO₂ with HEAL. The proposed model fits the experimental data of the enhancement factor due to the ready, chemical absorption of CO₂ in different solvents, temperatures, and HEAL concentrations. The reaction rate constant of CO₂ with HEAL was correlated linearly with the solubility parameter of the solvent.     

A Reusable Polymer-Anchored Palladium(II) Schiff Base Complex Catalyst for the Suzuki Cross-Coupling,Heck and Cyanation Reactions

A new polymer-anchored Pd(II) complex has been synthesized, characterized and its catalytic activity was investigated for the Suzuki cross-coupling reaction between aryl halides and arylboronic acid in the presence of K₂CO₃ as a base, for Heck olefination of aryl halides with alkenes, and for cyanation reaction of aryl iodides with K₄Fe(CN)₆ in presence of Et₃N as base. The key features of the catalyst include rapid reactions with excellent conversion without the use of phosphine ligands and total stability under the reactions conditions. The catalyst was recovered by simple filtration and reused five-times without significant loss of catalytic activity.     

Low-Temperature Sintering of (K0.5Na0.5)NbO3 Piezoelectric Ceramics

(K_0.5Na_0.5)NbO₃ piezoelectric ceramics can be sintered at a temperature as low as 750 °C for 5 h by incorporating Li₂CO₃ + Bi₂O₃ + ZnO as the sintering aid, whereas the conventional sintering temperature is around 1,100 °C. The optimal “soft” piezoelectric properties are obtained for ceramics sintered at 850 °C for 5 h. The dielectric permittivity (ε), piezoelectric coefficient (d ₃₃), electromechanical coupling (k _p) and mechanical quality factors (Q _m) of (K, Na)NbO₃ modified with 5.5 wt% sintering aids are 1,436, 90 pC/N, 0.3 and 10, respectively. These values are similar to the values obtained for (K_0.5Na_0.5)NbO₃ ceramics sintered above 1,100 °C. The underlying mechanism for abrupt change of dielectric permittivity is explained.     

An efficient microwave-assisted Suzuki reaction using Pd/MCM-41 and Pd/SBA-15 as catalysts in solvent-free condition

Palladium catalysts, Pd/MCM-41 and Pd/SBA-15 were prepared by impregnation of an aqueous solution of [Pd(NH₃)₄]Cl₂ on MCM-41 and SBA-15. Palladium contents of Pd/MCM-41 and Pd/SBA-15 are 8.4% and 8.7%, respectively. It has been shown that these catalysts are very suitable to microwave-assisted Suzuki reactions under solvent-free condition. It is also found that the base additives for this reaction are K₂CO₃, Cs₂CO₃ or CsF. Thus, phenylboronic acid and phenyl iodide with Pd/MCM-41 produce biphenyl by microwave irradiation for 10 min in 97.4% yield. Phenyl bromide, instead of phenyl iodide, also proceeds the reaction with phenylboronic acid using Pd/MCM-41 or Pd/SBA-15 yielding biphenyl by microwave irradiation for 10 min in excellent yield. Whereas the reaction of phenyl chloride with phenylboronic acid gives poor yield in same condition. Various aryl iodides and aryl bromides are tested. In this paper our recent results of microwave-assisted Suzuki reaction using Pd/MCM-41 and Pd/SBA-15 under solvent-free condition are described.     

Room-temperature Suzuki–Miyaura coupling of aryl bromides with phenylboronic acid catalyzed by a palladium complex with an inexpensive nitrogen-containing bis(phosphinite) ligand

A palladium(II) complex with a known inexpensive and very easily synthesized nitrogen-containing bis(phosphinite) ligand has been prepared and characterized by spectroscopic and crystallographic studies. The ligand is bound to the metal in a P,P-bidentate coordination mode with a bite angle of 98.90°. This complex was found to be an efficient catalyst for room-temperature Suzuki–Miyaura coupling of a variety of aryl bromides with phenylboronic acid. At 0.1 mol% of palladium in DMF/K₃PO₄ for 24 h, the corresponding biaryls were obtained with 75–92% yields. Activated substrates displayed high yields even within minutes.     

The effect of relative humidity on CO<Subscript>2</Subscript> capture capacity of potassium-based sorbents

Potassium-based sorbent was prepared by impregnation with potassium carbonate on activated carbon. The role of water and its effects on pretreatment and CO₂ absorption was investigated in a fixed bed reactor. K₂CO₃ could be easily converted into K₂CO₃·1.5H₂O working as an active species by the absorption of water vapor as the following reaction: K₂CO₃+3/2 H₂O→K₂CO₃·1.5H₂O. One mole of K₂CO₃·1.5H₂O absorbed one mole of CO₂ as the following reaction: K₂CO₃·1.5H₂O+CO₂ai2KHCO₃+0.5 H₂O. The K₂CO₃·1.5H₂O phase, however, was easily transformed to the K₂CO₃ phase by thermal desorption even at low temperature under low relative humidity. To enhance CO₂ capture capacity and CO₂ absorption rate, it is very important to maintain the K₂CO₃·1.5H₂O phase worked as an active species, as well as to convert the entire K₂CO₃ to the K₂CO₃·1.5H₂O phase during CO₂ absorption at a temperature range between 50 °C and 70 °C. As a result, the relative humidity plays a very important role in preventing the transformation from K₂CO₃·1.5H₂O to the original phase (K₂CO₃) as well as in producing the K₂CO₃·1.5H₂O from K₂CO₃, during CO₂ absorption between 50 °C and 70 °C.     

Role of Temperature in the Structure of Zn(II)-1,4,-BDC Metal-Organic Frameworks and their Adsorption and Diffusion Properties for Carbon Dioxide

The role of reaction temperature in the structure of Zn(II)-1,4,-Benzendicarboxylic-MOFs (Zn-BDC-MOFs) and subsequently their CO₂ adsorption properties were investigated. Crystal morphology and phase structure of the Zn-BDC-MOFs were characterized by SEM and PXRD. Stability and textual properties of the Zn-BDC-MOFs were analyzed by using accelerated surface area and porosimetry apparatus (ASAP) and thermogravimetric analysis (TG). Adsorption equilibrium and diffusion of CO₂ on these materials were experimentally studied by the gravimetric method in the pressure range up to 1 atm at room temperature. Results showed that reaction temperature changed the coordination mode of 1,4,-Benzendicarboxylic acid ligand and caused the different structures and pore texture of Zn-BDC-MOFs. High reaction temperature was good for the generation of the three-dimensional MOFs with a higher adsorption capacity for CO₂ but lower gas diffusivity. In contrast, low reaction temperature could cause the monodentate ligand in metal centers and form the low-dimensional MOFs with a lower adsorption capacity for CO₂ but higher gas diffusivity. The order of CO₂ adsorption uptake and diffusion time constant were given as MOF-130T > MOF-50T > MOF-100T > MOF-75T and MOF-50T > MOF-75T > MOF-100T > MOF-130T, respectively.     

Cu-ZSM5 as reusable catalyst for the one-pot,odorless and ligand-free C-S bond formation

Cu^I-ZSM5 and Cu^II-ZSM5 as reusable and heterogeneous nanocatalysts were synthesized and characterized using various techniques. The catalysts have been applied for the practical synthesis of various phenyl aryl/benzyl sulfides via one-pot and odorless processes from the reaction of triphenyltin chloride or phenylboronic acid as phenyl source with different aryl/benzyl halides in the presence of S₈ as sulfur source and KF or KOH as S₈ activator in DMF at 80 °C.     

Synthesis and characterization of some new aromatic polytriazoles as proton conductive membranes

A series of new poly(1,2,4-triazole)s (PTAs) containing pyridine heterocyclic ring, bearing bulky aromatic pendent groups, were synthesized from the reaction of the corresponding polyhydrazides with aniline or 4-aminobenzenesulfonic acid in polyphosphoric acid (PPA) at 175 °C. The non-sulfonated PTAs showed glass transition temperatures (T _gs) of 220–250 °C and inherent viscosities (η _inh) equal to 0.48–0.78 dL/g, and the sulfonated poly(1,2,4-triazole)s (S-PTAs) exhibited T _gs of 235–265 °C and inherent viscosities equal to 0.50–0.83 dL/g. The former polymers were soluble in conc. H₂SO₄ and partially soluble in hot N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), and 1-methyl-2-pyrrolidone (NMP), and the latter were soluble in DMF, NMP, DMSO and DMAc at room temperature. All polymers had useful levels of thermal stability and were stable up to 450 °C in nitrogen. The proton conductivities of undoped sulfonated polytriazole membranes and the acid-doped sulfonated polytriazole membranes lie in the range of 5 × 10^?4–8.1 × 10^?3 and 5 × 10^?3–2.3 × 10^?2 S/cm, respectively, at 90 °C and 100 % relative humidity.     

RAFT-mediated synthesis of poly(N-(2-hydroxypropyl)methacrylamide-b-4-vinylpyridine) by conventional and microwave heating

We report the synthesis of N-(2-hydroxypropyl)methacrylamide (HPMA) macroCTA and HPMA-b-4-Vinylpyridine block copolymers via reversible addition-fragmentation chain transfer (RAFT) reaction. Polymerization was carried out in dimethylformamide (DMF) at 70 °C using 4-Cyano-4(thiobenzoylthio) pentanoic acid as chain transfer agent and AIBN as an initiator. Control over molecular weight and composition was achieved by altering the CTA, monomer and initiator feed ratio. The controlled living character of the polymerization was verified with pseudo-first-order kinetic plots, a linear increase of the molecular weight with conversion, and low polydispersities (PDIs ≤ 1.2). Effect of microwave heating on the homo- and copolymer formation was investigated and the rates were significantly higher than those observed under conventional heating conditions. These polymerization reactions were in controlled fashion resulting in polymers with low PDIs, too. These polymers have a great potential to be used in developing delivery vehicles and conjugates for further drug or gene delivery applications.     

Synthesis of a new “green” sponge via transesterification of dimethyl carbonate with polyvinyl alcohol and foaming approach

In this article, the low toxicity of polyvinyl alcohol (PVA) and dimethyl carbonate (DMC) were used to synthesize polyvinyl alcohol carbonate (PVAC) sponge via a simple transesterification-foaming approach, and the structure and morphology of PVAC sponge were characterized; moreover, the influence of dosage of K₂CO₃, PVA, distilled water and n-pentane on the water retention capacity of PVAC sponge were investigated, and the influence of reaction temperature and reaction time on the water retention capacity of PVAC sponge were also surveyed. Based on those, it was confirmed that 9.00 g PVA and 5.00 mL DMC in the presence of 2.00 g K₂CO₃ and 50.00 mL water could be used to synthesize PVAC polymer at 75?°C and for 2.5 h via the transesterification approach, and PVAC polymer in the presence of 5.00 mL n-pentane could be used to synthesize PVAC sponge at 55?°C and for 10 h via the foaming approach, and PVAC sponge owned the structure of six-membered lactone ring and the polyporous morphology, and the maximal water retention capacity was 21.50 g/g.     

Supramolecular Chemistry of Organoplatinum(IV) Complexes Bearing Ligands with Remote Carboxylic Acid Substituents

The oxidative addition of compounds RBr to [PtMe₂(bpox)], 1, bpox = 2,5-bis(2-pyridyl)-1,3,4-oxadiazole gave the corresponding organoplatinum(IV) complexes [PtBrMe₂(R)(bpox)], 2, R = CH₂CO₂H; 3, R = CH₂-4-C₆H₄CO₂H; 4, R = CH₂-4-C₆H₄CH₂CO₂H, whereas the reaction with BrCH₂CH₂CO₂H gave only the platinum(II) complex [PtBrMe(bpox)], 5. The organoplatinum(IV) complexes with carboxylic acid substituents form unusual supramolecular structures in the solid state through hydrogen bonding interactions, some of which are supramolecular polymers.     

Screening test for aqueous solvents used in CO2 capture: K2CO3 used with twelve different rate promoters

K₂CO₃ solution is widely used in the CO₂-capture industry. In particular, it has advantages for treating CO₂ in flue gas under high-temperature and high-pressure conditions. However, it has a lower CO₂-loading capacity and slower absorption kinetics than those of amines, which are its major disadvantages. Thus, in this study, we investigated ten loading-rate promoters, five primary amines and five secondary amines, to develop higher CO₂-loading capacity and faster absorption kinetics. The screening tests of the absorption and desorption processes were conducted at 70 °C and 90 °C, respectively. Based on the results, we concluded that all the amines used improved the CO₂-loading and absorption kinetics compared with the use of K₂CO₃ alone. At a certain value CO₂ loading, the respective performance of the primary and secondary amines was twice and thrice better, respectively, than the neat K₂CO₃ solution. Thus, secondary amines had superior absorption capacity and absorption/desorption rate compared to primary amines. Among the secondary amines, pipecolic acid, sarcosine, and isonipecotic acid were determined as the most effective absorption rate promoters.     

CO2 absorption properties of Brønsted acid-base ionic liquid composed of N,N-dimethylformamide and bis(trifluoromethanesulfonyl)amide

The solubilities of CO₂ and the liquid densities in a Brønsted acid-base ionic liquid, [DMFH][Tf₂N], composed of N,N-dimethylformamide (DMF) and bis(trifluoromethanesulfonyl)amide (HTf₂N) have been investigated at high pressures and at different temperatures. The results were compared with those in DMF and a typical 1-butyl-3-methylimidazolium analogue with the same anion, [BMIM][Tf₂N]. The mole fraction scaled solubilities of CO₂ in the three liquids showed a slight increase in the following order, DMF < [DMFH][Tf₂N] < [BMIM][Tf₂N], whereas more remarkable difference was observed in the volume scaled concentrations of CO₂, [BMIM][Tf₂N] < [DMFH][Tf₂N] « DMF, mainly due to the bulkiness of liquid entities.     

Reduction of CO2 to CO at Cu–ceria-gadolinia (CGO) cathode in solid oxide electrolyser

The feasibility was investigated of using a Cu/CGO cathode for CO₂ reduction to CO in a high temperature solid oxide electrolyser (CO₂–CO, Cu/CGO|YSZ|YSZ/LSM|LSM, ambient air). An adherent layer of porous Cu/CGO electrode on YSZ electrolyte was achieved by sintering Cu/CGO paste at 1,000 °C for 5 h. Comparable performance was obtained with Ni/YSZ and Cu/CGO cathodes for CO₂ reduction at 750 °C and a 50:50 CO₂–CO feed; CO oxidation rates were faster than CO₂ reduction rates. Ohmic and polarisation resistances of the Cu/CGO electrode all decreased with decreasing CO₂:CO feed ratio. In the electrolytic mode, 100 % current efficiency for CO₂ reduction to CO was achieved on the Cu/CGO cathode at potential differences up to 1.5 V, above which the electronic conductivity of the YSZ electrolyte increased, causing a loss in effective current efficiency. Further increase in potential difference to ca. >2.3 V caused irreversible damage to the YSZ electrolyte due to its partial decomposition. No significant performance degradation, Cu sintering/migration, carbon deposition or electrode delamination was evident during 2 h of operating the electrolyser at 1.85 V and 750 °C for CO₂ reduction with a Cu/CGO cathode.     

Amination of glycidyl methacrylate-grafted polystyrene particles and their adsorption capacity for Nd3+ and Cd2+

A new chelating adsorbent was prepared by grafting glycidyl methacrylate (GMA) onto polystyrene (PS) particles using simultaneous radiation technique and amination of graft copolymers by reacting with diethylenetriamine. The effects of various parameters such as, irradiation doses, inhibitor concentrations, amination temperature, and reaction time were investigated. The grafting yield increased with irradiation dose to reach its maximum value at 15 kGy. The accelerative effect of solvent medium on the grafting yield was higher in THF than DMF. The addition of 0.001 % (wt) inhibitor to the reaction medium led to a sharp increase of grafting yield. The best conversion ratio was obtained at 115 °C during 24 h. By using a column separation technique, the adsorption behaviors of the adsorbent toward Cd²⁺ and Nd³⁺ in aqueous solution were examined. The adsorption amount of both Cd²⁺ and Nd³⁺ increased with initial ions concentration. The maximum equilibrium of Cd²⁺ and Nd³⁺ adsorbed ions were 18.1 and 17.58 mg/g, respectively. It was observed that the functionalized GMA-g-PS was reusable by desorbing with 0.1 M nitric acid almost without losing their adsorption capacity. FTIR test indicates that epoxide and amine groups were introduced onto GMA-g-PS and aminated GMA-g-PS, respectively. The T _g of graft copolymer slightly decreased, and that of aminated GMA-g-PS was higher than graft copolymer.