A highly regio‐ and enantioselective cobalt‐catalyzed sequential hydrosilylation/hydrogenation of alkynes was developed to afford chiral silanes. This one‐pot method is operationally simple and atom ...economic. It makes use of relatively simple and readily available starting materials, namely alkynes, silanes, and hydrogen gas, to construct more valuable chiral silanes. Primary mechanistic studies demonstrated that highly regioselective hydrosilylation of alkynes with silanes occurred as a first step, and the subsequent cobalt‐catalyzed asymmetric hydrogenation of the resulting vinylsilanes showed good enantioselectivity.
We're in this together: A novel regio‐ and enantioselective cobalt‐catalyzed sequential hydrosilylation/hydrogenation of alkynes was developed. This one‐pot method is operationally simple and atom economic. It makes use of relatively simple and readily available starting materials to construct more valuable chiral silanes, which can be further functionalized to diverse silicon‐containing chiral compounds.
Epoxy resins are very important and widely used thermosetting polymers that find many practical applications. Very often their properties can be effectively modified by an addition of reactive ...silanes, polysiloxanes, silsesquioxanes, silica, montmorillonite, and other fillers. This review considers the literature concerning: (a) synthesis of carbofunctional silanes (CFS), polysiloxanes (CFPS) and polyhedral silsesquioxanes (POSS); (b) properties of neat epoxy resins and their composites and nanocomposites, obtained by modifications with reactive silanes, silicon containing monomers and polymers, and silica based fillers, enabling improvement of their mechanical properties, thermal and flame resistance as well as providing corrosion and antimicrobial protection.
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•The fundamental aspects of wettability and surface tension phenomena are presented and discussed.•The latest etching developments and recent promising applications are discussed.•The ...advantages and drawbacks of superhydrophobic materials of preparation have been identified.•The rugosity of the surface is crucial to obtain a superhydrophobic surface.•Optically transparent and highly stable superhydrophobic coatings are needed to protect solar cells.
With the recent progress in nanotechnology and material engineering, nano-based coatings have become multifunctional, smarter, efficient, versatile and durable. Superhydrophobic coatings are an important class of the smart coating family, which has gained recognition in coating science over the last few years. The uniqueness of superhydrophobic coatings arises from the various phenomenal innovations, and its development is expected to continue in the next decades. The bioinspired superhydrophobic surfaces are commonly obtained by designing a double-scale structure by using nanotechnology, followed by the addition of water repellent compounds. It lacks an overview article describing on the recent progress in superhydrophobic coatings and surfaces. In this perspective article, various fundamental aspects of wettability and related phenomena are discussed. We present and compare the existing methods for the preparation of superhydrophobic coatings. Properties of superhydrophobic coatings such as self-cleaning, anti-icing, anti-fouling, and anti-bacterial features were also introduced. The review also discusses various superhydrophobic technological breakthroughs and future trends in the preparation and application of these materials.
The reaction of trans‐M(N2)2(dppe)2 (M=Mo, 1Mo, M=W, 1W) with B(C6F5)3 (2) provides the adducts (dppe)2M=N=N‐B(C6F5)3 (3) which can be regarded as M/B transition‐metal frustrated Lewis pair (TMFLP) ...templates activating dinitrogen. Easy borylation and silylation of the activated dinitrogen ligands in complexes 3 with a hydroborane and hydrosilane occur by splitting of the B−H and Si−H bonds between the N2 moiety and the perfluoroaryl borane. This reactivity of 3 is reminiscent of conventional frustrated Lewis pair chemistry and constitutes an unprecedented approach for the functionalization of dinitrogen.
Dinitrogen is one of the missing small‐molecule targets of the frustrated Lewis pair (FLP) chemistry. The use of a Group 6 metal (Mo or W)/boron comound allows activation of N2 that is reminiscent of conventional FLPs. This mode of activation allows its mild and easy borylation and silylation, under a mechanism in which coordinated N2 acts as the Lewis base component of an FLP.
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A simple chemical synthetic route was designed to prepare zinc oxide nanoparticles (ZnO-NPs) by using sodium alginate as anti-agglomeration agent in the presence of sodium hydroxide ...as alkali. Next, surface modification of ZnO-NPs with SiO2 nanoparticles was achieved as per to sol-gel process. Further enhancing of the multifunctional properties of SiO2@ZnO-NPs was conducted successfully thanks to (aminopropyl)triethoxysilan (APTES) and vinyltriethoxysilan (VTES) which, in turns, increase the affinity of the SiO2@ZnO-NPs nanocomposite towards glycosidic chains of cotton fabrics. Thorough characterizations of synthesized ZnO-NPs, SiO2@ZnO-NPs, SiO2@ZnO-NPs/APTES and SiO2@ZnO-NPs/VTES were conducted by the making use of well advanced techniques such as FT-IR, XRD, TEM, DLS and SEM-EDX. The data obtained clarified the formation of an interfacial chemical bond between ZnO and SiO2 as affirmed by FT-IR and XRD analysis. In addition, the results revealed by TEM, zeta sizer and SEM-EDX techniques, declared that the amorphous layers of SiO2, APTES or VTES evenly coated the surface of ZnO-NPs. For these nanocomposites, the work was extended to render cotton fabrics multifunctional properties such as antibacterial and UV protection with high durability even after 20 washing cycles using pad dry cure method. Taking the advantages of the silane compounds terminated by active groups such as OH, NH2, etc., open the door for further functionalization of the cotton fabrics’ surfaces by durable multifunctional agents applied in various applications.
Catalytic C(sp3)−O bond cleavage promoted by B(C6F5)3 /Et3SiH proceeds preferentially with primary tosylates in the presence of primary and secondary silyl ethers and aryl ethers. This reactivity ...difference enables the chemoselective defunctionalization of several 1,n‐diols, and the efficiency of the new procedure is highlighted by the selective deoxygenation of the hydroxymethyl group of an orthogonally protected carbohydrate. Tosylates with an adjacent phenyl group are cleaved with anchimeric assistance.
The weakest link: Hydrosilanes activated by B(C6F5)3 are known to cleave ethers as well as silyl ethers. However, more reactive tosylates are cleaved prior to those ethers, which allows for the chemoselective deoxygenation of diols and polyols. Other functional groups such as carboxyl groups are also tolerated. Defunctionalization of phenethyl tosylate motifs proceeds with anchimeric assistance (rearrangement).
Schematic illustration for the synthesis of the POS@HNTs and the superhydrophobic POS@HNTs surfaces fabricated by spray-coating (the blue-colored globule represents water droplet on the surfaces).
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•Halloysite nanotubes (HNTs) were treated by n-hexadecyltriethoxylsilane and tetraethoxysilane.•Superhydrophobic coating was fabricated by spray-coating polysiloxane modified HNTs.•Silane affects transparency, morphology, and superhydrophobicity of HNTs coating.•HNTs coatings exhibit super self-cleaning and oil/water separation functions.
Superhydrophobic coatings with high water contact angles, ultralow sliding angles, excellent stability, oil/water separation, and self-cleaning functions were fabricated by spray-coating the suspensions of polysiloxane modified halloysite nanotubes (POS@HNTs) onto various substrates. The hydrophobic treatment of HNTs was performed by hydrolytic co-condensation of n-hexadecyltriethoxylsilane and tetraethoxysilane on the surfaces of the HNTs. A thick POS layer is located on the surfaces of the HNTs, which makes HNTs hydrophobic. The POS@HNTs were characterized using scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy and thermogravimetric analysis. The effects of the ratio of silane and HNTs on the transparency, morphology, and wettability of the coatings were investigated. The transparency of the coating decreases with the increase in the silane loading. The water contact angles of the POS@HNTs coating increase with the increase in the silane loading, but the water sliding angles of the coatings are nearly independent on their ratio. The stability, oil/water separation, and self-healing capability of the coatings were also studied. The coatings on different substrates show high contact angle towards different liquid, e.g. 1 M HCl, 1 M NaOH, tea, and milk. Also, the POS@HNTs coated meshes can efficiently separate oils from water with high separation efficiency. In addition, the POS@HNTs coated gloves show a self-cleaning effect. All these results suggest that the POS@HNTs exhibit great potential for their application in waterproof materials, self-cleaning coating, and oil/water separation devices.
The first electrochemical hydrolysis of hydrosilanes to silanols under mild and neutral reaction conditions is reported. The practical protocol employs commercially available and cheap NHPI as a ...hydrogen‐atom transfer (HAT) mediator and operates at room temperature with high selectivity, leading to various valuable silanols in moderate to good yields. Notably, this electrochemical method exhibits a broad substrate scope and high functional‐group compatibility, and it is applicable to late‐stage functionalization of complex molecules. Preliminary mechanistic studies suggest that the reaction appears to proceed through a nucleophilic substitution reaction of an electrogenerated silyl cation with H2O.
A practical electrochemical method for selective hydrolysis of hydrosilanes to furnish diverse silanols has been achieved. These reactions occur with high chemoselectivity and functional‐group tolerance under mild and neutral reaction conditions. The addition of NHPI as a HAT mediator is crucial for promoting the generation of silyl cation species.
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•Silanized microcristallyne cellulose were study in this paper.•The best APTES/MCC ratios was determined.•Samples showed an independence of activation energy (Ea) from conversion ...degree (α).•The degradation model proposed in this paper were: A→B→C.•The degradation mechanism was modified from 5 silane ratio.
Microcrystalline cellulose (MCC) can be a reinforcement in composites, especially after surface modification. In this paper, MCC was modified using 3-aminopropyltriethoxysilane (APTES) in the following ratios (MCC/APTES): 1:3, 1:4, 1:5, 1:10). The MCC morphologies did not change with the treatment even though the distribution of APTES over the MCC surface varied. FTIR analysis showed MCC and APTES characteristic peaks for all samples. The crystallinity index (CI) decreased with the APTES ratio. The non-isothermal kinetic degradation by thermogravimetric analysis in different heating rates was studiedin order to evaluate the kinetic triplet: activation energy Ea, exponential factor (A), and reaction order (f(α)). The Ea dependence on conversion degree was not affected, but two degradation steps were observed for all samples. Ratios up to 1:4 suggested two consecutive autocatalytic degradation mechanisms. The 1:5 and 1:10 ratios caused a change in the most probable degradation mechanism for nucleation followed by autocatalytic degradation mechanism.
No neutral silicon Lewis super acids are known to date. We report on the synthesis of bis(perchlorocatecholato)silane and verify its Lewis super acidity by computation (DLPNO‐CCSD(T)) and experiment ...(fluoride ion from SbF6−). The exceptional affinity towards donors is further demonstrated by, for example, the characterization of an unprecedented SiO4F2 dianion and applied in the first hydrodefluorination reaction catalyzed by a neutral silicon Lewis acid. Given the strength and convenient access to this new Lewis acid, versatile applications might be foreseen.
Neutral, but super attractive: Bis(perchlorocatecholato)silane is the first neutral silicon Lewis super acid. The Lewis acidity is exemplified by coordination of weak donors, halide ions, and a catalytic hydrodefluorination reaction.
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