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Metal confinement catalyst MoS2/Pt@TD-6%Ti (TD, TS-1/Dendritic mesoporous silica nanoparticles composite) in dendritic hierarchical pore structures was synthesized and showed excellent sulfur-resistance performance and stabilities in catalytic hydrodesulfurization reactions of probe sulfide molecules. The MoS2/Pt@TD-6%Ti catalyst combines the concepts of Pt-confinement effect and hydrogen spillover of Pt noble metal. The modified micropores of Mo/Pt@TD-6%Ti only allow the migration and dissociation of small H2 molecules (0.289 nm), and effectively keep the sulfur-containing compounds (e.g. H2S, 0.362 nm) outside. Thus, the MoS2/Pt@TD-6%Ti catalyst exhibits higher DBT and 4,6-DMDBT HDS activities because of the synergistic effect of the strong H2 dissociation ability of Pt and desulfurization ability of MoS2 with a lower catalyst cost. This new concept combining H2 dissociation performance of noble metal catalyst with the desulfurization ability of transition metal sulfide MoS2 can protect the noble metal catalyst avoiding deactivation and poison, and finally guarantee the higher activities for DBT and 4,6-DMDBT HDS.

A dendritic PdCu/Ce0.3Zr0.7O2 (PdCu/CZ-3) catalyst with uniform spherical morphology was prepared for boosting the catalytic performance of CO2 hydrogenation to methanol (MeOH). The open dendritic pore channels and small particle sizes could reduce not only the diffuse resistance of reactants and products but also increase the accessibility between the active sites (PdCu and oxygen vacancy) and the reactants (H2 and CO2). More spillover hydrogen could be generated due to the highly dispersed PdCu active metals over the PdCu/CZ-3 catalyst. PdCu/CZ-3 can stimulate the generation of more Ce3+ cations, which is beneficial to produce more oxygen vacancies on the surface of the CZ-3 composite. Spillover hydrogen and oxygen vacancy could promote the formate and methoxy routes over PdCu/CZ-3, the primary intermediates producing MeOH. PdCu/CZ-3 displayed the highest CO2 conversions (25.5 %), highest MeOH yield (6.4 %), highest PdCu-TOFMeOH (7.7 h-1) and superior 100 h long-term stability than those of other PdCu/CexZr1-xO2 analogs and the reference PdCu/CeO2 and PdCu/ZrO2 catalysts. Density functional theory (DFT) calculations and in situ DRIFTS were performed to investigate the CO2−MeOH hydrogenation mechanism.

A novel dendritic composite (TD) with an open center-radial pore structure using TS-1 nanocrystals as microporous precursors was successfully synthesized by a facile method. TS-1 nanocrystals were embedded into the framework of dendritic mesoporous silica nanospheres (DMSNs) to form Si–O–Ti bonds, which was beneficial for generating more S vacancies of MoS2 active phases. The NiMo/TD-2 catalyst had a larger surface area and stronger metal–support interaction, resulting in higher sulfidation and dispersion degrees of MoS2 active phases over the sulfided NiMo/TD-2 catalyst, which was consequently favored to improve the hydrodesulfurization (HDS) activity of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Furthermore, the NiMo/TD-2 catalyst with an SiO2/TiO2 molar ratio of 150 exhibited higher HDS performance for DBT and 4,6-DMDBT than other NiMo/TD catalysts and the commercial NiMo/Al2O3 catalyst. Moreover, the NiMo/TD-2 catalyst possessed more Bronsted and Lewis acid sites, thus promoting the hydrogenation of DBT and the isomerization of 4,6-DMDBT.

FeCuCo over aluminum oxide catalyst was prepared to catalytically degrade polystyrene (PS) into ethylbenzene (EB) under mild conditions. This catalyst was characterized by XRD, SEM, STEM-EELS, STEM-EDS, XPS, and physical properties. A significant selectivity toward EB formation at 250 °C was achieved in the absence of hydrogen with 82% liquid yield. End-chain session and cross-linking reactions are proposed to be the dominant pathways in the degradation of PS over FeCuCo to form EB. Keywords: Polystyrene, Catalytic-degradation, Ethylbenzene, Selective-conversion

Advances in processing capabilities of computer clusters have allowed for the full modeling of organometallic complexes that previously would have been simplified to reduce computational cost. Increased feasibility of computational modeling offers new challenges, not only in terms of limitations of methods and theory, but attention should be paid to complexes that can exist in many conformations, as the appropriate choice of conformer may be easily overlooked. In this work a series of pincer complexes with isopropyl and cyclopentyl substituents have been chosen as examples to demonstrate the importance of conformational analysis. The complexes examined contain four isopropyl or cyclopentyl groups on phosphor atoms generating between 27 and 324 possible rotamers. The importance of conformational search in a mechanistic investigation is demonstrated with the CO2 insertion into a nickel hydride bond of POCOP iPr nickel hydride complex. Results show that the reaction energy profile can be both exergonic and endergonic depending on rotamer choice. Specifically, the POCOPiPr Ni-formato complex product of the CO2 insertion reaction had an energy difference between the lowest and highest energy rotamer as high as 16.8 kcal/mol. The significant energy differences between rotamers highlight the importance of thorough conformational analysis and should be taken into consideration when evaluating the energy profile of related reactions. Keywords: Conformational analysis, DFT, Pincer, Mechanism, Rotamers

High-pressure H2 was produced by the selective dehydrogenation of formic acid (DFA) using ruthenium complexes at mild temperatures in various organic solvents and water. Among the solvents studied, 1,4-dioxane was the best candidate for this reaction to generate high gas pressure of 20 MPa at 80 °C using the Ru complex having a dearomatized pyridine-based pincer PN3P* ligand. This complex shows reusability for the high-pressure DFA in 1,4-dioxiane while maintaining the catalytic performance, however, deactivation occurred in other solvents. In dimethyl sulfoxide, its decomposition products may cause catalytic deactivation. The gas pressure generated in 1,4-dioxane was lower than that in water due to the high dissolution of 1,4-dioxane into CO2 according the vapor-liquid equilibrium calculations. The role of solvent is crucial since it affected the catalytic performance and also the generated gas pressure (H2 and CO2) from FA.

Formic acid possesses many desirable properties as a promising hydrogen energy carrier. Density functional theory (DFT) was utilized to design new Rh complexes with 2,2′-biimidazoline ligands to explore their potential as catalysts for formic acid dehydrogenation. These designed complexes were prepared and examined as catalysts under various temperatures and ratios of formic acid to sodium formate. It was found that although our complexes gave a high TOF of 20,000 h−1 at 90 °C under certain formic acid/sodium formate ratios, the dehydrogenation reaction was prematurely deactivated once 30% of the formic acid was consumed. Possible deactivation mechanisms were investigated by NMR and HRMS. Our observations suggest that while guided rational design of catalysts by DFT has much potential, the method does have limitations as evidenced by our experimental comparisons and thus pure DFT design should be conducted with caution.

LaFeO3 was prepared via simple, economical and environmentally friendly auto-combustion methods using different fuels, including citrate, urea, sucrose, egg whites, gelatin and chitosan. The prepared ferrites were systematically characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, high resolution transmission electron microscopy (HRTEM), vibrating sample magnetometry (VSM) and electrical measurements to study the impact of the synthetic routes on the various properties. XRD showed the formation of a single orthorhombic phase, except for the samples prepared via egg white, gelatin and urea methods, which indicated a secondary La2O2CO3 phase. The FT-IR and TEM studies confirmed the formation of the phase. Differential thermal analysis-thermogravimetry techniques (DTA-TG) were used to characterize the auto-combustion process up to ferrite formation. The obtained unsaturated magnetization for all of the samples suggested the presence of anti-ferromagnetic ordering in addition to weak ferromagnetic ordering. The egg white method showed higher magnetization (1.78 emu/g), while the urea and chitosan methods indicated lower magnetization (0.13 emu/g). The coercivity measurements confirmed the presence of ferromagnetic/anti-ferromagnetic interfaces with higher values than those reported in the literature. The AC-conductivity measurements indicated semiconducting characteristics and exhibited a change in the conduction mechanism from hopping to polaron conduction by increasing the temperature. LaFeO3 prepared via the egg white method indicated an anti-ferromagnetic/paramagnetic transition at approximately 715 K. The dielectric measurements confirmed the AC-conductivity results and exhibited values higher than those reported in the literature.

The aim of this work is to prepare catalysts for energy efficient conversion of polystyrene (PS) and its waste into valuable products with high conversion at 250 °C. The FeCo/Alumina bimetallic catalyst was synthesized by aqueous impregnation and structurally determined using scanning-transmission electron microscopy, temperature programmed desorption, X-ray diffraction, and X-ray photoelectron spectroscopy. Successfully, we have achieved up to 91% liquid yield with selectivities for styrene monomer (SM) up to 45 wt% and ethylbenzene (EB) up to 55 wt%, depending on the exposure time at 250 °C by FeCo/Alumina which is comparable to those of reactions at high temperatures (≥350 °C). Further increase of catalyst loadings from 200 to 400 mg also led to the decrease in styrene yield and increase in ethylbenzene yield. The analysis of the resulting clear liquid by gas chromatography/mass spectrometry (GC/MS) indicates the generation of products in the gasoline range.

Tumor tissue biopsies are invasive, costly, and collect a limited cell population not completely reflective of patient cancer cell diversity. Circulating tumor cells (CTCs) can be isolated from a simple blood draw and may be representative of the diverse biology from multiple tumor sites. The VTX-1 Liquid Biopsy System was designed to automate the isolation of clinically relevant CTC populations, making the CTCs available for easy analysis. We present here the transition from a cutting-edge microfluidic innovation in the lab to a commercial, automated system for isolating CTCs directly from whole blood. As the technology evolved into a commercial system, flexible polydimethylsiloxane microfluidic chips were replaced by rigid poly(methyl methacrylate) chips for a 2.2-fold increase in cell recovery. Automating the fluidic processing with the VTX-1 further improved cancer cell recovery by nearly 1.4-fold, with a 2.8-fold decrease in contaminating white blood cells and overall improved reproducibility. Two isolation protocols were optimized that favor either the cancer cell recovery (up to 71.6% recovery) or sample purity (≤100 white blood cells/mL). The VTX-1's performance was further tested with three different spiked breast or lung cancer cell lines, with 69.0% to 79.5% cell recovery. Finally, several cancer research applications are presented using the commercial VTX-1 system.

We report here a direct knitting Method for preparation of highly robust, effective while air- and moisture-tolerant, and readily recyclable three-dimensional (3D) porous polymer-Pd network (PPPd) from the widely used Pd(PPh 3 ) 4 . Electro-beam induced Pd atom crystallization was observed for the first time in organic polymer and revealed the ultrafine dispersion of palladium atoms. Challenging types of Suzuki-Miyaura couplings, reductive coupling of aryl halides and oxidative coupling of arylboronic acid were successively catalyzed by PPPd in aqueous media. Also catalytically selective C H functionalization reactions were achieved with orders of magnitude more efficient than conventional Pd homogeneous catalysts. The strategy developed here provides a practical method for easy-to-make yet highly efficient heterogeneous catalysis.

A post-modification strategy is used to synthesize a new class of diimine-amido PN3P-pincer group-10 transition metal complexes. The coordination chemistry and the thermal stabilities of their organometallic derivatives are characterized and investigated.

Mechanistic insights into the selective C–H terminal activation of n -pentane with tungsten allyl nitrosyl complex reported by Legzdins were gained by employing density functional theory with B3LYP hybrid functional. Using Bader’s atom in molecules (AIM) analysis on the elementary steps of the hydrogen transfer process, TS1 and TS2 , it was observed that the calculated H-transfer models were closely similar to Hall’s metal-assisted σ-bond metathesis through bond critical point (BCP) comparisons. One distinguishable feature was the fact that the formal oxidation state of the W changed in the concerted H-transfer process. To better differentiate, we term these processes as ‘Formal Reductive Hydrogen Transfer’ (FRHT) for TS1 and ‘Formal Oxidative Hydrogen Transfer’ (FOHT) for TS2 .

There exists a strong demand to replace expensive noble metal catalysts with efficient and earth-abundant catalysts for hydrogen evolution reaction (HER). Recently the Co- and Mo-based sulfides such as CoS2, Co9S8, and MoSx have been considered as several promising HER candidates. Here, a highly active and stable hybrid electrocatalyst 3D flower-like hierarchical Co9S8 nanosheets incorporated with MoSx has been developed via a one-step sulfurization method. Since the amounts of Co9S8 and MoSx are easily adjustable, we verify that small amounts of MoSx promotes the HER activity of Co9S8, and vise versa. In other words, we validate that symmetric synergy for HER in the Co- and Mo-based sulfide hybrid catalysts, a long-standing question requiring clear experimental proofs. Meanwhile, the best electrocatalyst Co9S8-30@MoSx/CC in this study exhibits excellent HER performance with an overpotential of −98 mV at −10 mA/cm2, a small Tafel slope of 64.8 mV/dec, and prominent electrochemical stability.

In this study, we report the direct synthesis of amides and ureas via the catalytic dehydrogenation of volatile alcohols and amines using the Milstein catalyst in a Pd-Ag/ceramic membrane reactor. A series of amides and ureas, which could not be synthesized in an open system by catalytic dehydrogenation coupling, were obtained in moderate to high yields via catalytic dehydrogenation of volatile alcohols and amines. This process could be monitored by the hydrogen produced. Compared to the traditional method of condensation, this catalytic system avoids the stoichiometric pre-activation or in situ activation of reagents, and is a much cleaner process with high atom economy. This methodology, only possible by employing the Pd-Ag/ceramic membrane reactor, not only provides a new environmentally benign synthetic approach of amides and ureas, but is also a potential method for hydrogen storage.

While recent reports have demonstrated that oxide-derived Cu-based electrodes exhibit high selectivity for CO 2 reduction at low overpotential, the low catalytic current density ( 2 at −0.45 V vs . RHE) still largely limits its applications for large-scale fuel synthesis. Here we report an extremely high current density for CO 2 reduction at low overpotential using a Cu foam electrode prepared by air-oxidation and subsequent electroreduction. Apart from possessing three-dimensional (3D) open frameworks, the resulting Cu foam electrodes prepared at higher temperatures exhibit enhanced electrochemically active surface area and distinct surface structures. In particular, the Cu foam electrode prepared at 500 °C exhibits an extremely high geometric current density of ~9.4 mA/cm 2 in CO 2 -saturated 0.1 M KHCO 3 aqueous solution and achieving ~39% CO and ~23% HCOOH Faradaic efficiencies at −0.45 V vs . RHE. The high activity and significant selectivity enhancement are attributable to the formation of abundant grain-boundary supported active sites and preferable (100) and (111) facets as a result of reconstruction of Cu surface facets. This work demonstrates that the structural integration of Cu foam with open 3D frameworks and the favorable surface structures is a promising strategy to develop an advanced Cu electrocatalyst that can operate at high current density and low overpotential for CO 2 reduction.

Tuning the pore structure of zeolitic imidazolate frameworks (ZIFs) enables unique control of their material properties. In this work, we used computational methods to examine the gate structure of ZIF-8 tuned by substitution terminal groups. The substitution position and electron affinity of the added groups were shown to be key factors in gate size. Electrostatic interactions are responsible for the variation in gate opening. These results suggest that the post-modification of terminal group in ZIFs can be used to finely tune the pore gate, opening up new strategies in the design of ZIFs with desired properties.

Most oxygen evolution reaction (OER) electrocatalysts are not stable in corrosive acids. Even the expensive RuO 2 or IrO 2 , the most acid-resistant oxides, can be dissolved at an oxidative potential. Herein, we realize that the failures of OER catalysts are mostly caused by the weak interface between catalysts and the substrates. Hence, the study of the interface structure between catalysts and substrates is critical. In this work, we observe that the cheap OER catalysts Co 3 O 4 can be more durable than the state-of-the-art RuO 2 if the interface quality is good enough. The Co 3 O 4 nanosheets deposited on carbon paper (Co 3 O 4 /CP) is prepared by electroplating of Co-species and followed by a two-step calcination process. The 1st step occurs in vacuum in order to maintain the surface integrity of the carbon paper and converts Co-species to Co(II)O. The 2nd step is a calcination in ambient conditions which enables the complete transformation of Co(II)O to Co 3 O 4 without degrading the mechanical strength of the Co 3 O 4 -CP interface. Equally important, an in situ formation of a layer of amorphous carbon on top of Co 3 O 4 further enhances the OER catalyst stability. Therefore, these key advances make the Co 3 O 4 catalyst highly active toward the OER in 0.5 M H 2 SO 4 with a small overpotential (370 mV), to reach 10 mA/cm 2 . The observed long lifetime for 86.8 h at a constant current density of 100 mA/cm 2 , is among the best of the reported in literature so far, even longer than the state-of-art RuO 2 on CP. Overall, our study provides a new insight and methodology for the construction of a high-performance and high stability OER electrocatalysts in corrosive acidic environments.

A series of oxazadisilinane compounds were prepared and used as Bronsted bases to form a series of 21 siloxane protic ionic liquids (Si-PILs) with four different acids. This new family of Si-PILs were well characterized and examined to catalyze esterification reactions.

Summary Chiral phosphoric acid-catalyzed highly enantioselective formal [3 + 2] cycloaddition reaction of azoalkenes with 3-vinylindoles has been established. Under mild conditions, the projected cycloaddition proceeded smoothly, affording a variety of 2,3-dihydropyrroles in high yields and excellent enantioselectivities, and also in a diastereospecific manner. As opposed to the common 4-atom synthons in the previous literature reports, azoalkenes served as 3-atom synthons. Besides, the observed selectivity was supported by primary theoretical calculation. The unique chemistry of azoalkenes disclosed herein will empower asymmetric synthesis of nitrogen-containing ring structural motifs in a broader context., Graphical Abstract, Highlights • Chiral phosphoric acid catalyzed formal [3 + 2] cycloaddition reaction • 2,3-Dihydropyrroles were enantioselectively synthesized • Azoalkenes served as 3-atom synthons, Organic Chemistry; Organic Synthesis; Physical Organic Chemistry

Although chemical bath of TiCl4 treatment has been used to serve as a compact layer for planar perovskite solar cells (PSCs), uneven TiO2 particle sizes and chlorine residual would decrease the device performance. In this study, we modify the TiCl4 treatment process through well-controlled the kinetics grown of TiO2 nanoparticle, leading to a uniform and ultrathin TiO2 blocking layer. A dense and pinholeless TiO2 blocking layer is crucial for high-performance PSCs because of its effective charge extraction and elimination of carrier shunting path. The as-fabricated devices using modified process of TiO2 blocking layer exhibit the best power conversion efficiency (PCE) of 17.89% with an average PCE of 17.5%. Scanning electron microscopy and cyclic voltammetry analysis of TiO2 blocking layer reveal that this process improved surface uniformity and the carrier blocking capability.

Push–pull type porphyrin-based sensitizers have become promising candidates for high-efficiency dye sensitized solar cells (DSCs). It is of importance to understand the fundamental structure-physical property-photovoltaic performance relationships by varying the donor and acceptor moieties. In this work, two new porphyrin-based sensitizers, WW-7 and WW-8, were synthesized and compared with the known sensitizer YD20. All the three dyes have the same porphyrin core and acceptor group (ethynylbenzoic acid) but their donor groups vary from the triphenylamine in YD20 to meso-diphenylaminoanthracene in WW-7 to N-phenyl carbazole in WW-8. Co(II/III)-based DSC device characterizations revealed that WW-7 showed enhanced light harvesting ability in comparison to YD20 with improved incident photon-to-collected electron conversion efficiencies (IPCEs). As a result, WW-7 displayed much higher short circuit current (Jsc: 13.54 mA cm−2) and open-circuit voltage (Voc: 0.829 V), with a power conversion efficiency (η) as high as 7.7%. Under the same conditions, YD20 cell exhibited a power conversion efficiency of 6.6% and the dye WW-8 showed even lower efficiency (η = 4.6%). Detailed physical measurements and theoretic calculations were conducted to understand the difference and reveal how three different donor structures affect their molecular orbital profile, light-harvesting ability, energy level alignment, and eventually the photovoltaic performance.

Incomplete oxidation of (N-di-tert-butylphosphino)-6-(2-methyl-2′H-benzoimidazole)-2-aminepyridine dichlorocobalt (PN3CoCl2) in DMF results in a unique co-crystal I formed with three parts including DMF, unit A and unit B complex with Co1 and Co2, respectively (PN3 ligand in unit A: (N-di-tert-butylphosphino)-6-(2′-methyl-2′H-benzoimidazole)-2-aminepyridine, and O PN3 ligand in unit B: (N-di-tert-butylphosphinoxide)-6-(2′-methyl-2′H-benzoimidazole)-2-aminepyridine), with 1:1:1 molar ratio. Co1 and Co2 complexes both display a five-coordinated distorted-square-pyramidal geometry around the metal center. The Co1 center is coordinated with PN3 ligand via two N atoms from pyridine, benzoimidazole moiety as well as one P atom, and the Co2 center is coordinated with the oxidized ligand O PN3 via two N atoms from pyridine, benzoimidazole moiety as well as one O atom from DMF molecule, while the oxidized phosphine moiety (O P) being excluded from the coordination sphere. Activated with AlEt2Cl, the co-crystallized complexes I are able to actively convert butadiene to polybutadiene, affording cis-1,4 polybutadiene with cis-1,4 unit up to 95.5–97.8% and number average molecular weight of cal. 105 g/mol. The high cis-1,4 selectivity and monomodal GPC curve of resultant polymer imply that the identical active species generated from two distinctive cobalt centers.

Tridentate complexes Cr(III)Cl3L, [L = 2,6-bis(dimethyl-2-oxazolin-2-yl) pyridine], Fe(III)Cl3L, Fe(II)Cl2L and Co(II)Cl2L have been prepared and fully characterized. The solid structures of Cr(III)Cl3L, Fe(III)Cl3L and Co(II)Cl2L have been revealed by single crystal X-ray diffraction, and the Cr(III)Cl3L and Fe(III)Cl3L complexes both exhibit a distorted octahedral geometry, while the Co(II)Cl2L complex has a trigonal bipyramidal conformation. Four complexes have been examined in regioselective polymerization of butadiene in combination with MAO in toluene at room temperature. The trans-1,4, cis-1,4 enchainment of resultant polybutadiene are controlled by the metal center. Activated by MAO, complex Cr(III)Cl3L produces high level of trans-1,4 selectivity (trans-1,4 up to 93.3%) with moderate polymer yield, complexes Fe(III)Cl3L and Fe(II)Cl2L both show equal cis-1,4 and trans-1,4 with minor 1,2 selectivity (

There exists a strong demand to replace expensive noble metal catalysts with cheap metal sulfides or phosphides for hydrogen evolution reaction (HER). Recently metal phosphides such as NixP, FeP and CoP have been considered as promising candidates to replace Pt cathodes. Here we report that the nanocrystalline CoP nanosheet assembly on carbon cloth can be formed by a two-step process: electrochemical deposition of Co species followed by gas phase phosphidation. The CoP catalyst in this report exhibits a Tafel slope of 30.1 mV/dec in 0.5 M H2SO4 and 42.6 mV/dec in 1 M KOH. The high HER performance of our CoP catalysts is attributed to the rugae-like morphology which results in a high double-layer capacitance and high density of active sites, estimated as 7.77×1017 sites/cm2.

Work on a new class of PN 3 -pincer ligands for metal–ligand cooperative catalysis is reviewed. While the field of the pyridine-based PN 3 -transition metal pincer complexes is still relatively young, many important applications of these complexes have already emerged. In several cases, the PN 3 -pincer complexes for metal–ligand cooperative catalysis result in significantly improved or unprecedented activities. The synthesis and coordination chemistry of PN 3 -pincer ligands are briefly summarized first to cover the synthetic routes for their preparation, followed by a focus review on their applications in catalysis. A specific emphasis is placed on the later section about the role of PN 3 -pincer ligands’ dearomatization–rearomatization steps during the catalytic cycles. The mechanistic insights from density functional theory (DFT) calculations are also discussed.

Chromium (III) complexes, Cr1, [2,6-(tBu2PNH)2C5H4N]CrCl3; Cr2, [2,6-(Ph2PNH)2C5H4N]CrCl3; Cr3, [2-(tBu2PNH)C5H4N]CrCl3 THF; Cr4, [6-(tBu2PNH)C5H4N-2-CH2NEt2]CrCl3; Cr5, [6-(tBu2PNH)C5H4N-2-C3H2N2]CrCl3; Cr6, [6-(tBu2PNH)C5H4N-2-(3,5-Me2)C3H2N2]CrCl3; Cr7, [6-(tBu2PNH)C5H4N-2-(3,5-iPr2)C3H2N2]CrCl3; Cr8, [6-(tBu2PNH)C5H4N-2-(3,5-Ph2)C3H2N2]CrCl3, bearing a family of neutral PN3-type pincer ligands have been prepared. The molecular structure of Cr2 was further elucidated by the X-ray crystallographic analysis, showing an octahedral geometry. Treatment of these complexes with MAO or alkylaluminum led to catalysts with moderate activities (about 105 g (PE)/Cr(mol) h) for ethylene polymerization, affording exclusively linear low molecular weight solid PE without any detectable oligomers. Among Cr1–Cr8, the highest activity was achieved for Cr1/MAO at room temperature with production of PE with highest molecular weight, indicating that replacement of both tBu groups in Cr1 with Ph groups, or one PtBu2 with the N (imine) arm, resulted in a lower catalytic activity and lower Mw.

NiAgPd nanoparticles are successfully synthesized by in-situ reduction of Ni, Ag and Pd salts on the surface of carbon. Their catalytic activity was examined in ammonia borane (NH3BH3) hydrolysis to generate hydrogen gas. This nanomaterial exhibits a higher catalytic activity than those of monometallic and bimetallic counterparts and a stoichiometric amount of hydrogen was produced at a high generation rate. Hydrogen production rates were investigated in different concentrations of NH3BH3 solutions, including in the borates saturated solution, showing little influence of the concentrations on the reaction rates. The hydrogen production rate can reach 3.6–3.8 mol H2 molcat−1 min−1 at room temperature (21 °C). The activation energy and TOF value are 38.36 kJ/mol and 93.8 mol H2 molcat−1 min−1, respectively, comparable to those of Pt based catalysts. This nanomaterial catalyst also exhibits excellent chemical stability, and no significant morphology change was observed from TEM after the reaction. Using this catalyst for continuously hydrogen generation, the hydrogen production rate can be kept after generating 6.2 L hydrogen with over 10,000 turnovers and a TOF value of 90.3 mol H2 molcat−1 min−1.

A high-surface-area Cu electrode, fabricated by a simple electrochemical anodization-reduction method, exhibits high activity and selectivity for CO2 reduction at low overpotential in 0.1 M KHCO3 solution. A faradaic efficiency of 37% for HCOOH and 27% for CO production was achieved with the current density of 1.5 mA cm−2 at −0.64 V vs. RHE, much higher than that of polycrystalline Cu. The enhanced catalytic performance is a result of the formation of the high electrochemical active surface area and high density of preferred low-index facets. Keywords: CO2 reduction, Cu electrode, High-surface-area, High selectivity

Iron(II) complexes, [Fe(2,6-bis(4,4-dimethyl-1,3-oxazolin-2-yl)pyridine)Cl 2 ] ((Fe(Me 2 –pybox)Cl 2 ), 3 ) and [Fe(2,6-bis(4,4-diphenyl-1,3-oxazolin-2-yl)pyridine)Cl 2 ] ((Fe(Ph 2 –pybox)Cl 2 ), 4 ), have been synthesized and characterized by X-ray crystallographic analysis. Upon treatment of complex 3 with silver triflate and 4 with acetonitrile, [Fe(Me 2 –pybox)(CH 3 CN)OTf 2 ] ( 5 ) and [Fe(Ph 2 –pybox)(CH 3 CN) 2 Cl][FeCl 3 ] ( 6 ) were obtained, respectively. The bulkier phenyl substitutes were found not only to cause the elongation of the N–Fe bonds but also influence the reactivity of the Fe center.

Tridentate chromium complexes (Cr1–Cr7) incorporated with symmetrical pincer ligand bis(arylimino)pyridine and bis(pyrzaolyl)pyridine have been synthesized and characterized by elemental analyis, FT-IR as well as ESI-MS. X-ray diffraction reveals solids-state structures of Cr2, Cr4 and Cr6 all adopt pseudo-octahedral coordination environment with respect to metal center. All complexes have been tested in stereoregulated polymerization of butadiene under various polymerization conditions. The trans-1,4 and cis-1,4 enchainment of resultant polymer are found to be dependent on the structure of ligand and amount of activator used. Under the optimized condition, free ortho-substitutes Cr catalysts Cr1, Cr3, Cr4 and Cr6 are capable of initiating high trans-1,4 selectivity (trans-1,4: 89.2%–92.0%) with good polymer yields (71.5%–78.0%), while counterparts with ortho-positioned alkyl groups Cr2, Cr5 and Cr7 display mixed selectivities with moderate polymer yields. The sterical effect of ligand and amount of MMAO on the catalytic performance, in particular, the stereoselectivity and polymer yield, has been also elucidated by conjugated diene polymerization mechanism.

The reaction of RhCl3·H2O with tBu2P(CH2)5PtBu2 afforded several complexes including [RhIII(H)Cl{tBu2P(CH2)2CH(CH2)2PtBu2}] (1), [RhIIIHCl2{tBu2P(CH2)5PtBu2}]2 (2), [RhICl{tBu2P(CH2)2CH CHCH2PtBu2}] (3) and [RhICl{tBu2PCH2C(O)CH CHCH2PtBu2}] (4). X-ray crystal structures of 3 and 4 showed that the C C bond on the C5 unit of tBu2P(CH2)5PtBu2 is bound to Rh(I) in a η2 configuration. In 4, the Rh atom has a trigonal pyramidal coordination geometry. The X-ray crystal structure of 2 consists of two rhodium(III) centers bridged by two tBu2P(CH2)5PtBu2 ligands with two phosphorus atoms, one from each ligand, trans to one another. The crystal structure of the rhodium oxygen adduct with 1,3-bis(di-t-butylphosphinomethyl)benzene [RhO2{tBu2PCH2(C6H3)CH2PtBu2}] (5) was also investigated. In this species the O2 is η2 coordinated to the Rh(I) center with asymmetric Rh–O bond lengths (2.087(7) and 1.998(8) A). The O–O bond distance is short (1.337(11) A) with νO–O of 990.5 cm−1. DFT calculations on complex 5 yielded two η2–O2 structures that differed in energy by only 0.76 kcal/mol. The lower energy one (5a) had near C2 symmetry, and had nearly equal Rh–O bond lengths, while the higher energy structure (5b) had near Cs symmetry and generally good agreement with the experimental structure. The calculated UV–Vis and IR spectra of complex 5 are in excellent agreement with experiment.

The direct palladium-catalyzed coupling of polyfluoroarenes with aryltrifluoroborates gave the desired products of fluorinated biaryls in good to excellent yields. A diverse set of important functional groups including methoxy, aldehyde, ester, nitro and halide can be well tolerated in the protocol.

A copper-catalyzed method for the trifluoromethylation of arylsulfinates with Togni's reagent has been developed, affording aryltrifluoromethylsulfones in moderate to good yields. A wide range of functional groups in arylsulfinates are compatible with the reaction conditions.

Nanoscale scratches are applied using an atomic force microscope (AFM) to investigate the mechanical aspect of the material removal process in chemical–mechanical polishing. The scratching experiments are carried out with the AFM, whose probe has an SiO2 particle (radius ~ 400 nm) bonded to it, at low normal forces in deionized (DI) water and a slurry. The experimental results show that the scratch depth increases with increasing normal force. Under a constant force, the scratch depth of the surface in the slurry is significantly larger than that in DI water. This is due to a soft passivation layer generated during chemical interactions on the copper surface. The passivation layer significantly affects the coefficient of friction (COF) and wear rate. At a low scratch depth (below 20 nm), the COF obtained in DI water is ~ 1.74 times larger than that obtained in the slurry. The wear rate obtained in the slurry is larger than that obtained in the DI water.

A new method for the synthesis of trifluoromethylated acetylenes is developed which involves the copper-catalyzed trifluoromethylation of alkynyltrifluoroborates with an electrophilic trifluoromethylating reagent. This method offers significant advantages such as efficiency and mild and base-free reaction conditions. A plausible mechanism is proposed.

An efficient room temperature copper-catalyzed trifluoromethylation of organotrifluoroborates under the base free condition using an electrophilic trifluoromethylating reagent is demonstrated. The corresponding trifluoromethylarenes were obtained in good to excellent yields and the reaction tolerates a wide range of functional groups.

Well-defined PNNCN pincer ruthenium complexes bearing both strong phosphine and weak oxazoline donors were developed. These easily accessible complexes exhibit significantly better catalytic activity in transfer hydrogenation of ketones compared to their PN3P analogs. These reactions proceed under mild and base-free conditions via protonation–deprotonation of the ‘NH’ group in the aromatization–dearomatization process.

Two types of POCOP–nickel(II) pincer complexes were prepared by mixing POCOP pincer ligands and NiX2 in toluene at reflux. The resulting nickel complexes efficiently catalyze the homocoupling reactions of benzyl halides in the presence of zinc. The coupled products were obtained in excellent to quantitative yields.