Catalytic Activity of High-Surface-Area Amorphous MgO Obtained from Upsalite

The first aim of the research was to synthesize a pure Upsalite, which is an amorphous form of MgCO3, by modifying a procedure described in the literature, so that it would be the precursor of a high-surface, amorphous magnesium oxide. The results indicate that within the studied reaction conditions, the type of alcohol used as the reactant has the most pronounced effect on the yield of reaction. From the two alcohols that led to the highest yield of Upsalite, methanol gave a substantially larger surface area (794 vs. 191 m2 g−1). The optimized synthesis conditions of Upsalite were used to obtain MgO via thermolysis, whose activity in the transfer hydrogenation reaction (THR) from ethanol, 2-propanol and 2-pentanol to various carbonyl compounds was determined. The optimal conditions for the thermolysis were as follows: vacuum, T = 673 K as the final temperature, and a heating rate of 2 deg min−1. The high-surface, amorphous magnesia (SBET = 488 m2 g−1) was found to be a very selective catalyst to 4-t-butylcyclohexanone in THR, which led to a diastereoselectivity of over 94% to the E-isomer of 4-t-butylcyclohexanol for more than 3 h, with conversions of up to 97% with either 2-propanol or 2-pentanol as the hydrogen donor. In the case of acrolein and 2-n-propylacrolein being used as the hydrogen acceptors, the unsaturated alcohol (UOL) was the main product of the reaction, with higher UOL yields noted for ethanol than 2-propanol.

Antimicrobial Activities of Co (III), Mono and Tri-nuclear Ni Complexes Containing Schiff base Functionalized Imidazolium based Ligands

We reported the antimicrobial activities of cobalt and nickel complexes containing imino-NHC ligands. Complex 2 was synthesized by direct reaction of the insitu generated free carbene from 2-[2-(3-benzylimidazol-1-yl)ethyliminomethyl]phenol ligand with NiCl2 diglyme while complexes 3-5 were previously reported as catalysts in the transfer hydrogenation reaction of ketones. The compounds 1-5 were screened for antimicrobial sensitivity test against four gram-negative bacteria Escherichia Coli (E-coli), Shigella, Klebsiella Pneumoniae (K. Pneumoniae) and Salmonella Typhi (S.Typhi) and a gram positive bacteria Staphylocossus aureus (S.aureus). At a varying concentrations of 100, 200, 300, 400 and 500 µg/mL, significant activities were recorded using disc diffusion methods. The cobalt complex 3 was found to have higher activities compared with the corresponding nickel complexes and among the three nickel complexes, nickel complex with pyridine as wingtip was found to be more active than the one with a benzyl group. Similarly, the nickel centre with mononuclear was found to be more active than the tri-nuclear nickel complex. Except for the cobalt complex 3 no activity was recorded against S. typhi for all the nickel compounds.

A magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdII nanocomposite exhibiting facile tandem Suzuki coupling/transfer hydrogenation reaction

Herein, we report a magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdIINP (5) nanocomposite system for tandem Suzuki coupling/transfer hydrogenation reaction. The nanocomposite 5 was prepared first by making a layer of $$\hbox {SiO}_{2}$$ SiO 2 on $$\hbox {Fe}_{3}\hbox {O}_{4}\hbox {NP}$$ Fe 3 O 4 NP followed by deposition of $$\hbox {Pd}^{0}$$ Pd 0 and sorption of $$\hbox {Pd}^{\mathrm{II}}$$ Pd II ions successively onto the surface of Fe3O4@SiO2NP. The nanocomposite was characterized by powder XRD, electron microscopy (SEM-EDS and TEM-EDS) and XPS spectroscopy techniques. The mixed-valent $$\hbox {Pd}^{0}/\hbox {Pd}^{\mathrm{II}}$$ Pd 0 / Pd II present onto the surface of nanocomposite 5 was confirmed by XPS technique. Interestingly, the mixed-valent nanocomposite Fe3O4@SiO2/Pd0/PdIINP (5) exhibited tandem Suzuki coupling/transfer hydrogenation reaction during the reaction of aryl bromide with aryl boronic acid (90% of C). The nanocomposite 5 displayed much better reactivity as compared to the monovalent Fe3O4@SiO2/Pd0NP (3) (25% of C) and Fe3O4@SiO2/PdIINP (4) (15% of C) nanocomposites. Further, because of the presence of magnetic $$\hbox {Fe}_{3}\hbox {O}_{4}$$ Fe 3 O 4 , the nanocomposite displayed its facile separation from the reaction mixture and reused at least for five catalytic cycles.

Synthesis, Structure Determination and Catalytic Activity of a Novel Ruthenium(II) [RuCl(dppb)(44bipy)(4-pic)]PF6 Complex

This work reports the synthesis, structure and catalytic activity of a novel ruthenium(II) complex, [RuCl(dppb)(44bipy)(4-pic)]PF6 (where dppb = 1,4-bis(diphenylphosphine)butane; 44bipy = 4,4’-dimethyl-2,2’-dipyridyl; 4-pic = 4-picoline). The molecular structure and catalytic activity were studied by Fourier transform infrared (FTIR), UV-Vis and nuclear magnetic resonance (NMR) spectroscopies, cyclic voltammetry, and X-ray crystallography, while the electronic structure was investigated by density-functional theory (DFT) and time dependent DFT (TD-DFT) methods. Electrochemical studies showed the substitution of the chlorido ligand from the precursor by the 4-pic ligand, exhibiting the RuII/RuIII process at 1.21 V. The structure of the compound was optimized using DFT simulations and showed data similar to the X-ray structure. The UV-Vis absorption spectrum showed a good agreement with TD-DFT simulations. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies were determined at the Becke, 3-parameter, Lee-Yang-Parr (B3LYP) level. The study of the catalytic activity in the transfer hydrogenation of ketones by the 1H NMR showed efficient transfer hydrogenation reaction at 60 ºC, employing acetophenone as substrate and resulting in a high conversion. The formation of two ruthenium-hydride species was observed.

Ruthenium(ii)-catalyzed reductive N–O bond cleavage of N-OR (R = H, alkyl, or acyl) substituted amides and sulfonamides

A convenient method for the reductive cleavage of the N–O bonds of amide derivatives was developed using ruthenium(ii)-catalyzed transfer hydrogenation reaction.

Bis-NHC–Ag/Pd(OAc)2 Catalytic System Catalyzed Transfer Hydrogenation Reaction

The bis-NHC–Ag/Pd(OAc)2 catalytic system (NHC = N-heterocyclic carbene), a combination of bis-NHC–Ag complex and Pd(OAc)2, was found to be a smart catalyst in the Pd-catalyzed transfer hydrogenation of various functionalized arenes and internal/terminal alkynes. The catalytic system demonstrated high efficiency for the reduction of a wide range of various functional groups such as carbonyls, alkynes, olefins, and nitro groups in good to excellent yields and high chemoselectivity for the reduction of functional groups. In addition, the protocol was successfully exploited to stereoselectivity for the transformation of alkynes to alkenes in aqueous media under air. This methodology successfully provided an alternative useful protocol for reducing various functional groups and a simple operational protocol for transfer hydrogenation.

Synthesis of lignin-derived nitrogen-doped carbon as a novel catalyst for 4-NP reduction evaluation

In this study, nitrogen-doped carbon (NC) was fabricated using lignin as carbon source and g-C3N4 as sacrificial template and nitrogen source. The structural properties of as-prepared NC were characterized by TEM, XRD, FT-IR, Raman, XPS and BET techniques. Attractively, NC has proved efficient for reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using NaBH4 as hydrogen donor with high apparent rate constant (kapp = 4.77 min−1) and specific mass activity (s = 361 mol kgcat−1 h−1), which values are superior to the previously reported catalysts in the literature. Density functional theory (DFT) calculations demonstrate that four kinds of N dopants can change the electronic structure of the adjacent carbon atoms and contribute to their catalytic properties dependant on N species, however, graphitic N species has much greater contribution to 4-NP adsorption and catalytic reduction. Furthermore, The preliminary mechanism of this transfer hydrogenation reaction over as-prepared NC is proposed on the basis of XPS and DFT data. Astoundingly, NC has excellent stability and reusability of six consecutive runs without loss of catalytic activity. These findings open up a vista to engineer lignin-derived NC as metal-free catalyst for hydrogenation reaction.