Organosilicon compounds have been extensively utilized both in industry and academia. Studies on the syntheses of diverse organosilanes is highly appealing. Through‐space metal/hydrogen shifts allow ...functionalization of C−H bonds at a remote site, which are otherwise difficult to achieve. However, until now, an aryl to alkyl 1,5‐palladium migration process seems to have not been presented. Reported herein is the remote olefination, arylation, and borylation of a methyl group on silicon to access diverse vinyl‐, benzyl‐, and borylsilanes, constituting a unique C(sp3)−H transformation based on a 1,5‐palladium migration process.
Shifting positions: Reported here is the remote olefination, arylation, and borylation of a methyl group on silicon, constituting a unique C(sp3)−H transformation based on a 1,5‐palladium migration process. It provides a powerful and efficient synthetic method starting from simple unfunctionalized organosilanes and leading to diverse vinyl‐, benzyl‐, and borylsilanes.
Novel waterborne acrylic resin modified with glycidyl methacrylate (GMA) was successfully synthesized via homogeneous solution polymerization in isopropyl alcohol followed by solvent exchange with ...water. Aminopropyltriethoxysilane (KH-550), a silane coupling agent that can crosslink with resin and iron base material, was used as curing agent for solidifying this GMA modified resin. The cured mechanism of the coating was also investigated by 29Si nuclear magnetic resonance (29Si NMR) spectra and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The waterborne acrylic resin was sprayed on the iron base material and cured by KH-550 for 30 min at 100 °C to form the desired coating. The GMA and KH-550 were found to significantly decrease the curing temperature of this two-component waterborne resin. The thermal property of the coatings with different GMA loadings was investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The GMA enhanced the thermal stability of the coatings from 100 to 400 °C. The modification of GMA was found to reinforce significantly the mechanical properties of the coatings. The tensile strength of coating modified with 15 wt% GMA got a 78.65% improvement compared to that of unmodified resin. The surface hydrophobicity of the coatings does get affected by this modification. The contact angle got increased from 87.72°of the unmodified resin coating to 99.51°of coating modified with 15 wt% GMA. This work opens a new way to synthesize high performance waterborne acrylic resin and reports on the anti-flash corrosion of waterborne coatings on the iron base material surface.
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•Novel waterborne acrylic resin modified with glycidyl methacrylate (GMA) was synthesized.•Aminopropyltriethoxysilane (KH-550) was used as curing agent for solidifying this GMA modified resin.•GMA enhanced the thermal stability, surface hydrophobicity and mechanical properties of the coatings.•KH-550 improved the curing density of the coatings and anti-flash corrosion.
A three‐coordinate low‐spin cobalt(I) complex generated using a pincer ligand is presented. Since an empty dx2-y2
orbital is sterically exposed at the site trans to the N donor of an acridane moiety, ...the cobalt(I) center accepts the coordination of various donors such as H2 and PhSiH3 revealing σ‐complex formation. At this low‐spin cobalt(I) site, homolysis of H–H and Si−H bonds preferentially occurs via bimolecular hydrogen atom transfer instead of two‐electron oxidative addition. When the resulting CoII–H species was exposed to N2, H2 evolution readily occurs at ambient conditions. These results suggest single‐electron processes are favored at the structurally rigidified cobalt center.
Fits to a T: A three‐coordinate low‐spin cobalt(I) complex with an acridane‐based pincer ligand was synthesized. It reacts with H2 and PhSiH3 by σ‐complexation at the cobalt center, which has an empty dx2-y2
orbital. In this example, the homolysis of a σ‐bond by bimolecular hydrogen atom transfer (HAT) occurs rather than oxidative addition.
A PdII‐catalyzed ortho C−H alkoxycarbonylation reaction of aryl silanes toward active hexafluoroisopropyl (HFIP) benzoate esters has been developed. This efficient reaction features high selectivity ...and good functional‐group tolerance. Notably, given the general nature of the silyl‐tethered directing group, this method delivers products bearing two independently modifiable sites. NMR studies reveal the presence of hydrogen bonding between HFIP and a pyrimidine nitrogen atom of the directing group, and it is thought to be crucial for the success of this alkoxycarbonylation reaction.
Let's get active: The title reaction of aryl silanes to deliver active hexafluoroisopropyl (HFIP) benzoate esters features high selectivity and good functional‐group tolerance. This method yields products bearing two independently modifiable sites. NMR studies reveal the presence of hydrogen bonding between HFIP and a pyrimidine nitrogen atom of the directing group (DG), and it is thought to be crucial for the success of this alkoxycarbonylation reaction.
The weak interface bonding strength between organic fibers and inorganic cement is the main challenge for organic fiber-enhanced cement due to the lack of necessary physical and chemical affinity. In ...order to improve the interface bonding strength between polyvinyl alcohol (PVA) fibers and cement, SiO2 nanoparticles (SiO2 NPs) were grafted to high strength and high modulus PVA fibers using γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) as coupling agent. The grafted-PVA fibers were endowed with a Nano-rough surface and high chemical reactivity with cement. The orthogonal experimental results show that the optimal grafting rate between SiO2 NPs and PVA fibers was 8.5 wt% with reaction time of 2 h, reaction temperature of 110 °C, and catalyst weight percentage of 10 wt%. With SiO2-grafted PVA fibers as the enhancement, their tensile strength and pullout bonding strength in cement increased up to 21% and 43% compared with pure PVA fibers, respectively. The enhancement of interfacial behavior between PVA fiber and cement was further evidenced by the finite element analysis and simulation. In conclusion, grafting SiO2 NPs on PVA fibers can improve the interfacial bonding strength toward cement under small deformation, which implied the enhanced reinforcement and crack resistance for cement. This effect was primarily attributed to the synergistic friction and chemical bonding forces between SiO2 NPs and cement.
A new chemoselective reductive nitro‐Mannich cyclization reaction sequence of nitroalkyl‐tethered lactams has been developed. Relying on the rapid and chemoselective iridium(I)‐catalyzed reduction of ...lactams to the corresponding enamine, subsequent nitro‐Mannich cyclization of tethered nitroalkyl functionality provides direct access to important alkaloid natural‐product‐like structures in yields up to 81 % and in diastereoselectivities that are typically good to excellent. An in‐depth understanding of the reaction mechanism has been gained through NMR studies and characterization of reaction intermediates. The new methodology has been applied to the total synthesis of (±)‐epi‐epiquinamide in four steps.
Let′s all go Mannich! A new chemoselective reductive nitro‐Mannich cyclization sequence of nitroalkyl‐tethered lactams has been developed. Catalyzed by iridium(I) in the presence of a silane terminal reductant, the methodology allows direct and rapid access to alkaloid natural‐product‐like structures in good yield and typically in excellent diastereoselectivity. The methodology was applied to the synthesis of (±)‐epi‐epiquinamide.
Functionalization reactions of the refrigerants HFO‐1234yf (2,3,3,3‐tetrafluoropropene) and HFO‐1234ze (1,3,3,3‐tetrafluoropropene) were developed. The selectivity and reactivity towards CF3 groups ...of C−F activation reactions can be controlled by employing either a germane or a silane as the hydrogen source. Unique transformations were designed to accomplish consecutive hydrogermylation and C−F activation steps. This allowed for an unprecedented transformation of an olefinic C−F bond into a C−H bond by heterogeneous catalysis. These reactions are catalyzed by nanoscopic aluminum chlorofluoride (ACF) under very mild conditions.
Functionalizations of tetrafluoropropenes such as HFO‐1234yf were developed. The transformation of the CF3 group into an olefinic CF2 group was achieved at nanoscopic aluminum chlorofluoride (ACF) with silane. Consecutive hydrogermylation and C−F activation steps enabled the transformation of an olefinic C−F into a C−H bond.
•We made a tranparent super-hydrophilic glass coating via a silane coupling agent.•We used TEOS to enhance the adhesion force of the coating.•We fitted the exponential formulas describing the ...relation between contact angle values and the silane coupling agent’s concentrations.
The soiling of the photovoltaic (PV) modules’ front surfaces decreases the power generation efficiency a lot. In this paper, a novel self-cleaning (super-hydrophilic) glass coating material with double layers’ structure is prepared and the synthesis process is simple and low-price. This super-hydrophilic coating barely decreases the transparency of the glass above solar cells in the PV modules. It only reduces about 2.9% of transparency compared with original glass. Briefly, TEOS (Tetraethylorthosilicate) is skillfully utilized as hydrophobic interlayer, connected to the substrate surface and super-hydrophilic layer, whose effective component is a particular silane-coupling agent named as 2-acetoxy (polyethyleneoxy) propyl triethoxysilane (abbreviated as SIA). The interlayer has three advantages: firstly, after the TEOS hydrophobic layer is coated, SIA’s hydrophobic siloxane terminals assemble toward this layer; secondly, SIA’s steric hindrance would decrease obviously because most of the molecules assemble orderly on the interlayer; thirdly, TEOS provides much more grafting sites and more SIA molecules are grafted. Thus, with the increasing TEOS’s concentration, the SIA’s coating becomes firmer, and the SIA’s concentration influences the water contact angle (CA). When it is bigger than 2.5%, the CA is less than 10° and the surface turns to super-hydrophilic. Besides, according to the samples with different SIA’s concentration and contact angle value, a fitting curve whose R2 is higher than 0.95 is made. Based on this, the experimental contact angle value of a surface made from this SIA could be predicted. And the difference between experimental and theoretical contact angle value ranges from 1.11% to 5.88%.
Methods for the highly stereoselective and regiodivergent hydrosilylation of 1,3‐disubstituted allenes have been developed. The synthesis of E allylsilanes is accomplished with palladium NHC ...catalysts, and trisubstituted Z alkenylsilanes are accessed with nickel NHC catalysts. Unsymmetrically substituted allenes are well tolerated with nickel catalysis and afford Z alkenylsilanes. Evidence for a plausible mechanism was obtained through an isotopic double‐labeling crossover study.
Silanes with a choice: The hydrosilylation of 1,3‐disubstituted allenes, which have presented a notorious challenge for regioselective additions, can now be accomplished with outstanding levels of regio‐ and stereocontrol. By altering the metal catalyst and ligand structure, access to trisubstituted Z alkenylsilanes or trans allylsilanes is provided in a simple catalytic operation.
A nonwoven fabric with paperlike qualities composed of silicon nanowires is reported. The nanowires, made by the supercritical-fluid–liquid–solid process, are crystalline, range in diameter from 10 ...to 50 nm with an average length of >100 μm, and are coated with a thin chemisorbed polyphenylsilane shell. About 90% of the nanowire fabric volume is void space. Thermal annealing of the nanowire fabric in a reducing environment converts the polyphenylsilane coating to a carbonaceous layer that significantly increases the electrical conductivity of the material. This makes the nanowire fabric useful as a self-supporting, mechanically flexible, high-energy-storage anode material in a lithium ion battery. Anode capacities of more than 800 mA h g–1 were achieved without the addition of conductive carbon or binder.
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