Organosilicon Research Articles

Isotopic Labeling of Carbonate Solvents to Understand Gas Generation in Li-Ion Batteries and Gas Reduction by Fluorinated Organosilanes

Battery aging processes from cycling or storage at high temperatures, high voltages, and long times lead to significant degradation of the lithium-ion electrolyte, including decomposition to gaseous species. Gassing in battery pouch cells causes swelling, negatively impacting cell safety and performance. Development of electrolyte formulations that increase stability and reduce gassing is critical for next-generation battery applications and requires a greater understanding of the mechanisms of gas generation and reduction.Fluorinated organosilicon (OS) materials have been developed by Silatronix® to improve high temperature performance with significantly reduced gassing in high Ni battery systems.1 Utilization of a calibrated GC-TCD system allows the specific gas species to be identified and quantified but did not provide information on the mechanisms responsible for producing each species. To provide that information, studies using isotopically labeled carbonate solvents were conducted to identify the source for each gas species using a calibrated GC-MS system.2,3 Beyond identifying the gas species that evolve from particular carbonate solvents, these studies showed that the fluorinated organosilicon (OS) compounds reduce gassing (50-80% reduction depending on the specific OS formulation) by addressing all observed sources of gas during high temperature storage.2,3 The use of isotopically labeled carbonate solvents is extended within this study to provide insight into the origin of gas products and the nature of gas reduction by various OS materials under diverse aging conditions, including high temperature and fast charge cycling, as well as high temperature storage. This investigation includes multiple 13C-labeled electrolyte components including diethyl carbonate (DEC) and dimethyl carbonate (DMC) in addition to ethylene carbonate (EC). Carbonate-only electrolytes are compared to electrolytes containing OS compounds to gain insight into gas reduction mechanisms. Where possible, comparisons are made between different OS structures and popular commercial additives.Overall, this study builds on previous work to detail the origins of gassing from three common commercial carbonate solvents when combined in a complex electrolyte formulation under multiple test conditions and demonstrates that OS materials are highly effective gas-reducing components.

Influence of silanes on the hydration of cement by separating the cement into its individual phases

AbstractCementitious materials can be treated with organosilicon compounds (silanes) to achieve a water‐repellent effect. However, the influence of silanes on cement hydration is still not fully understood. For this reason, we studied the hydration of the main Portland cement phase (C3S ‐ tricalcium silicate) and the interaction with iBTES (isobutyltriethoxysilane), iOTES (isooctyltriethxysilane) and nOTES (n‐octyltriethoxysilane) by isothermal calorimetry and in‐situ X‐ray diffraction (XRD). The results show that C3S hydration is initially retarded and subsequently accelerated by iBTES and iOTES. In addition to the hydration process, the crystal growth of the portlandites (calcium hydroxide) is also affected by the silanes. The XRD results indicate that the portlandites grow significantly more plate‐like. In this context, the influence of the silanes on the portlandite crystallization was therefore also recorded in a special experimental setup. From the scanning electron microscope images it can be shown that all portlandite crystals grown in the presence of silanes have a platelike morphology. This is due to the fact that the hexagonal surfaces of the portlandite are covered by silanes and thus the growth direction of the crystals is affected. The modified portlandite crystals indicate that silanes also influence the microstructure of the cement paste and therefore its chemical and mechanical properties.

Air-Stable Ni Catalysts Prepared by Liquid-Phase Reduction Using Hydrosilanes for Reactions with Hydrogen.

The liquid-phase reduction method for the preparation of metal nanoparticles (NPs) by the reduction of metal salts or metal complexes in a solvent with a reducing agent is widely used to prepare Ni NPs that exhibit high catalytic activity in various organic transformations. Intensive research has been conducted on control of the morphology and size of Ni NPs by the addition of polymers and long-chain compounds as protective agents; however, these agents typically cause a decrease in catalytic activity. Here, we report on the preparation of Ni NPs using hydrosilane (Ni-Si) as a reducing agent and a size-controlling agent. The substituents on silicon can control not only the size but also the crystal phase of the Ni NPs. The prepared Ni NPs exhibited high catalytic performance for the hydrogenation of unsaturated compounds, aromatics, and heteroaromatics to give the corresponding hydrogenated products in high yields. The unique feature of Ni catalysts prepared by the hydrosilane-assisted method is that the catalysts can be handled under air as opposed to conventional Ni catalysts such as Raney Ni. Characterization studies indicated that the surface hydroxide was reduced under the catalytic reaction conditions with H2 at around 100 °C and with the assistance of organosilicon compounds deposited on the catalyst surface. The hydrosilane-assisted method presented here could be applied to the preparation of supported Ni catalysts (Ni-Si/support). The interaction between the Ni NPs and a metal oxide support enabled the direct amination of alcohols with ammonia to afford the primary amine selectively.

Ligand-modulated nickel-catalyzed regioselective silylalkylation of alkenes

Organosilicon compounds have shown tremendous potential in drug discovery and their synthesis stimulates wide interest. Multicomponent cross-coupling of alkenes with silicon reagents is used to yield complex silicon-containing compounds from readily accessible feedstock chemicals but the reaction with simple alkenes remains challenging. Here, we report a regioselective silylalkylation of simple alkenes, which is enabled by using a stable Ni(II) salt and an inexpensive trans−1,2-diaminocyclohexane ligand as a catalyst. Remarkably, this reaction can tolerate a broad range of olefins bearing various functional groups, including alcohol, ester, amides and ethers, thus it allows for the efficient and selective assembly of a diverse range of bifunctional organosilicon building blocks from terminal alkenes, alkyl halides and the Suginome reagent. Moreover, an expedient synthetic route toward alpha-Lipoic acid has been developed by this methodology.

Efficient Protosilylation of Unsaturated Compounds with Silylboronates over a Heterogeneous Cu3N Nanocube Catalyst

AbstractCopper-catalyzed protosilylation of unsaturated compounds with silylboronates has attracted attention for the production of organosilanes; however, the use of organic ligands or bases is unavoidable. Herein, we report a heterogeneous catalytic system for the protosilylation of unsaturated compounds with silylboronates under mild and additive-free conditions over copper nitride nanocubes (Cu3N NCs). This method can be applied to various substrates (e.g., alkynes, alkenes, or imines) to afford the corresponding organosilicon compounds. The Cu3N NC catalyst can be easily recovered and reused several times. Thus, the active and reusable Cu3N NC catalyst offers a green and sustainable method for efficient organosilane production.

Si-Cu contact mass for catalysis in coatings industry for oil and gas pipes

Two contact masses were obtained and analyzed for their catalytic properties in the production of hydrophobic coatings. These masses are based on the silicon-copper system and consist of 25%Cu-75%Si and 50%Cu-50%Si compositions. A standard method of copper(I) chloride reduction was optimized to obtain finely dispersed copper particles with high catalytic activity. It is shown that reduction is possible directly in contact with silicon, the resulting average diameter of copper particles is 5-10 microns in both contact masses (25%Cu-75%Si and 50%Cu-50%Si). A metallographic analysis revealed a loose morphology of the silicon-copper phase interfaces, which is necessary to enhance the catalytic activity of the contact masses. Local chemical analysis by scanning electron microscopy has established the ratio of the particle size of the initial polycrystals of copper chloride(I) and the resulting copper particles as a result of reduction on silicon. The process of deep reduction makes it possible to obtain particles up to 5 microns in size. These results provide useful insights into the formulation of coatings containing organosilicon compounds to reduce friction in hydrocarbon transport.

Catalytic Synthesis of Silanols by Hydroxylation of Hydrosilanes: From Chemoselectivity to Enantioselectivity.

As a crucial class of functional molecules in organosilicon chemistry, silanols are found valuable applications in the fields of modern science and will be a potentially powerful framework for biologically active compounds or functional materials. It has witnessed an increasing demand for non-natural organosilanols, as well as the progress in the synthesis of these structural features. From the classic preparative methods to the catalytic selective oxidation of hydrosilanes, electrochemical hydrolysis of hydrosilanes, and then the construction of the most challenging silicon-stereogenic silanols. This review summarized the progress in the catalyzed synthesis of silanols via hydroxylation of hydrosilanes in the last decade, with a particular emphasis on the latest elegant developments in the desymmetrization strategy for the enantioselective synthesis of silicon-stereogenic silanols from dihydrosilanes.

Nanocomposites Based on Multi-Walled Carbon Nanotubes, Magnetite Nanoparticles, and Core–Shell Molecularly Imprinted Polymers in Piezoelectric Sensors for the Determination of Macrolide Antibiotics

A piezoelectric sensor with a recognition layer based on magnetic carbon nanocomposites, including multi-walled carbon nanotubes, magnetic Fe3O4 nanoparticles, and polymer nanospheres with molecular imprints of erythromycin and azithromycin, obtained by the “core–shell” method, is developed. Silicon dioxide particles are used as cores, on the surface of which a shell molecularly imprinted with macrolides is synthesized by free radical polymerization or the sol–gel method. SiO2 particles are obtained by the Stober method by varying the ratio of reagents during the synthesis. The size of the cores and nanoparticles of molecularly imprinted polymers (MIP) is determined by atomic force microscopy, and the density and uniformity of the layer on the surface of magnetic carbon nanocomposites (MCNC) are determined by the piezoelectric quartz crystal microbalance method. The optimal ratio of the reagents (template : functional monomer : cross-monomer) is established by a spectrophotometric method during the synthesis of “core–shell” nanostructures by free radical polymerization. A thin shell of SiO2 with imprints of an antibiotic based on organosilicon compounds used in the synthesis of the core is formed by the sol–gel method on the surface of the silicon dioxide core. The sensor recognition layer is formed under the action of an external magnetic field. The dependence of the analytical signal of the sensor based on MIP@SiO2/MCNC on concentration is linear in the range 5–160 µg/mL for azithromycin and 10–160 µg/mL for erythromycin, and with a recognition layer based on SiO2@SiO2/MCNC, in the concentration range 20–400 µg/mL for erythromycin.

Ruthenium-Catalyzed Dehydrogenative Intermolecular O-H/Si-H/C-H Silylation: Synthesis of (E)-Alkenyl Silyl-Ether and Silyl-Ether Heterocycle.

Selective dehydrogenative silylation is one of the most valuable tools for synthesizing organosilicon compounds. In this study, a regio- and stereoselective ruthenium-catalyzed dehydrogenative intermolecular silylation was firstly developed to access (E)-alkenyl silyl-ether derivatives and silyl-ether heterocycles with good functional group tolerance. Furthermore, two pathways for RuH2(CO)(PPh3)3/NBE-catalyzed dehydrogenative intermolecular silylation of alcohols and alkenes as well as intermolecular silylation of naphthol derivatives were investigated with H2SiEt2 as the hydrosilane reagent.

Archeological wood conservation with selected organosilicon compounds studied by XFM and nanoindentation

Waterlogged wood conservation is a complex and challenging task. Detailed knowledge about the interactions between the applied chemicals and wood is necessary to ensure the effective and safe conservation of wooden artifacts. The present research aims to determine the mechanism of dimensional stabilization of archeological wood by organosilicon compounds using the combination of synchrotron-based X-ray fluorescence microscopy (XFM) and nanoindentation. Archeological oak wood was treated with methyltrimethoxysilane, (3-mercaptopropyl)trimethoxysilane, or 1,3-bis-[(diethylamino)-3-(propoxy)propan-2-ol]-1,1,3,3-tetramethyldisiloxane, which in previous studies were found to be more effective than other organosilicons in stabilizing wood dimensions. The XFM and nanoindentation results showed that all three organosilicons infiltrated wood cell walls and enhanced their mechanical properties. The XFM also showed that part of the chemicals filled some void spaces like cell lumina. Based on the results obtained here and in our previous research, it is determined that the mechanism of archeological wood dimensional stabilization by organosilicon treatment is complex and likely involves both filling cell lumina and infiltration into cell walls where organosilicons interact with wood polymers.

EVALUATION OF CLINICAL EFFECTIVENESS OF THE DRUG SILIOSTIN IN BROILER CHICKEN DYSCHONDROPLASIA

An experiment was conducted at the poultry farm "Ivanov A. S." to study the clinical effectiveness of the new osteotropic drug Siliostin in broiler chicken dischondroplasia. Siliostin is a complex pharmaceutical composition containing sources of organosilicon and inorganic compounds, flavonoids, organic acids, vitamins, and a range of osteotropic macro and microelements. Two groups of Cobb-500 crossbred broiler chickens were formed for the experiment experimental and control (n = 60). Over 21 days, the birds in the experimental group received Siliostin at a dose of 2% of the mass of consumed complete feed, while the control group chickens were fed only on the primary ration feeds. The therapeutic effectiveness of Siliostin was evaluated based on criteria such as clinical condition, flock integrity, body weight, and serum blood biochemistry indicators. It was established that the use of the drug in cases of clinical manifestation of dischondroplasia in broiler chickens contributes to the improvement of the physiological condition of sick birds, normalisation of indicators of biochemical homeostasis, and also has a positive effect on feed activity and intensive body weight gain. Moreover, after the end of the drug administration period and until the completion of the production cycle (60 days), the positive dynamics in the parameters mentioned above were maintained, and no repeated cases of dischondroplasia were observed in the experimental group of broilers.

Aerogel-Like Material Based on PEGylated Hyperbranched Polymethylethoxysiloxane.

Aerogels are a class of materials that have gained increasing attention over the past several decades due to their exceptional physical and chemical properties. These materials are highly porous, with a low density and high surface area, allowing for applications such as insulation, catalysis, and energy storage. However, traditional aerogels, such as pure silica aerogels, suffer from brittleness and fragility, which limit their usefulness in many applications. Herein, we have addressed this problem by using organosilicon compounds, namely polymethylsilsesquioxane derivatives, for the synthesis of aerogel-like materials. Specifically, we have developed a novel approach involving surfactant-free synthesis of microcapsules from partially PEGylated hyperbranched polymethylethoxysiloxane. Due to the highly diphilic nature of these compounds, they readily concentrate at the oil/water interface in aqueous emulsions encapsulating oil droplets. During the subsequent condensation, the organosilicon precursor is consumed for hexane encapsulation (yielding hollow microcapsules) followed by the formation of a continuous condensed phase. Concurrently, methyl groups ensure the hydrophobicity of the resulting materials, which eliminates the need of using additional reagents for their hydrophobization.

Novel construction and synthesis mechanism of b-axis oriented flower-like SAPO-11 molecular sieve in OSC-containing system for efficient hydroisomerization of long-chain n-alkanes

In view of the fact that different kinds of flower-like zeolites and materials have been synthesized for catalysis, but there are few reports on the construction of flower-like SAPO-11 molecular sieve. In this work, we successfully synthesized b-axis oriented flower-like SAPO-11 molecular sieve with multi-layered structure in the organosilicon compounds (OSC)-containing system for the first time. The morphology and b-axis thickness of SAPO-11 flakes were controlled and the tailored synthesis of b-axis oriented flower-like SAPO-11 with multi-layered structure was realized by adding [3-(trimethoxysilyl) propyl] octadecyl dimethyl ammonium chloride (DMC) into the synthesis system. The NiWS supported catalyst for hydroisomerization of n-hexadecane was prepared by using the synthesized flower-like SAPO-11 as support. Through a series of characterization techniques, the effects of morphological changes of SAPO-11 molecular sieve on the textural properties, acidity, element composition and silicon distribution of SAPO-11 molecular sieve were investigated, and the influence mechanism of morphological changes of the support on the active phase properties of the catalyst was studied. The formation mechanism of multi-layered flower-like SAPO-11 was proposed, the influence mechanism of the morphological change of the support on the catalytic performance of the catalyst and the catalytic reaction kinetics was investigated, and the structure–activity relationship between flower-like SAPO-11 and NiWS supported catalyst was systematically expounded. It provides a reference for enriching the morphological types of SAPO-11 molecular sieve and preparing catalyst for high-efficiency hydroisomerization of long-chain n-alkanes.

Rhodium-Catalyzed Addition of (Trialkylsilyl)arenes to Electrophiles via π-Coordination-Driven C-Si Bond Activation.

Aromatic organosilicon compounds serve as valuable synthons due to their diverse reactivities, excellent compatibility with various functional groups, and ready availability. However, (trialkylsilyl)arenes, despite their potential utility, are generally considered unsuitable substrates for transition-metal-catalyzed cross-coupling due to the low polarity of their covalent C(aryl)-Si bonds and the significant steric hindrance imposed by alkyl substituents. These factors render them inert toward reactions with transition metals, such as transmetalation and oxidative addition. In this study, we present a method for the rhodium-catalyzed addition of (trialkylsilyl)arenes to electrophiles via π-coordination-driven desilylation. We propose that a dicationic rhodium species activates the unbiased C(aryl)-Si bond, increasing its polarity by forming an η6-arene complex, thereby facilitating heterolysis. The resulting phenyl anion complex readily engages in addition reactions with external electrophiles, effectively forming C-C bonds. Through comprehensive computational studies, we have unraveled an unexpected stepwise pathway for desilylation with fluoride. This pathway involves the addition of fluoride to the aromatic ring, followed by a 1,2-migration of fluoride, ultimately culminating in the departure of fluorotrimethylsilane.

NBE-Controlled Palladium-Catalyzed Intermolecular Selective C-H Silylation of Boronic Acids.

An efficient palladium-catalyzed intermolecular selective C-H silylation of boronic acids is described. The combination of palladium catalyst with copper oxidant enables ortho-selective C-H silylation by employing hexamethyldisilane as the trimethylsilyl source, which relies on the control of NBE derivatives as a switch, thus providing straightforward access to divergent organosilicon compounds.

Rhodium-Catalyzed Hydrolytic Cleavage of the Silicon-Carbon Bond of Silacyclobutanes to Access Silanols.

Herein, we report the first rhodium-catalyzed hydrolytic cleavage of the silicon-carbon bond in silacyclobutanes using water as the reactant. A series of silacyclobutanes could be employed in this reaction in the presence of the Rh/BINAP complex, resulting in the corresponding silanols in good yields. Additionally, a chiral 1,1,4,4-tetraaryl-2,3-O-isopropylidene-l-threitol-derived phosphoramidite ligand could be used in this reaction to yield Si-stereogenic silanol with promising enantioselectivity.

Dinuclear Gold-Catalyzed para-Selective C-H Arylation of Undirected Arenes by Noncovalent Interactions.

The regioselectivity of C-H functionalization is commonly achieved by directing groups, electronic factors, or steric hindrance, which facilitate the identification of reaction sites. However, such strategies are less effective for reactants such as simple monofluoroarenes due to their relatively low reactivity and the modest steric demands of the fluorine atom. Herein, we present an undirected gold-catalyzed para-C-H arylation of a wide array of monofluoroarenes using air-stable aryl silanes and germanes at room temperature. A high para-regioselectivity (up to 98 : 2) can be realized by utilizing a dinuclear dppm(AuOTs)2 (dppm=bis(diphenylphosphino)methane) as the catalyst and hexafluorobenzene as the solvent. This provides a general and practical protocol for the concise construction of structurally diverse para-arylated monofluoroarenes through C-H activation manner. It features excellent functional group tolerance and a broad substrate scope (>80 examples). Besides, this strategy is also robust for other simple monosubstituted arenes and heteroarenes. Our mechanistic studies and theoretical calculations suggest that para-C-H selectivity arises from highly electrophilic and structurally flexible dinuclear Ar-Au(III)-Au(I) species, coupled with noncovalent interaction induced by hexafluorobenzene.

Novel application of potassium methylsiliconate in cement-based materials: Retarding of hydration process and improvement of compressive strength

The presented research investigates the application of the organosilicon compound named potassium methylsiliconate (MESI) as a set-retarding admixture for cement-based materials which also provides the strengthening effect. The study concerns the impact of three dosages of MESI (1%, 2% and 3% per cement mass) on the properties of the cement paste, mortar and concrete. The greatest delay of the setting time of cement CEM I 42.5 R and retardation effect, examined by manual Vicat apparatus, was observed for addition of 1% methylsiliconate. The beginning of the setting was prolonged to 23 h. The influence of potassium methylsiliconate on the kinetics of cement hydration was investigated by isothermal calorimetry. The calorimetric results disclosed significant extension of induction period during Portland cement hydration with addition of potassium methylsiliconate as an admixture. It is especially visible in case of addition of 1% of MESI. Moreover, tests performed at 30 °C, 40 °C and 50 °C showed that MESI can also delay the cement hydration at higher temperatures. The influence of potassium methylsiliconate on the compressive strength of cement mortar and concrete after 1, 2, 7, 28 days and72 days was also investigated. In the first days of hydration, the compressive strength of the materials was reduced, but after 28 days of curing the compressive strength was increased by 21% and 16% for cement mortar and concrete, respectively. The impact of MESI on the microstructure and pore size distribution of cement pastes in 2nd, 7th and 28th of hydration was examined by mercury intrusion porosimetry (MIP). The result showed significant delay in the development of the cement pastes microstructure during the first days of hydration. The XRD and DTA/TG analysis provided the knowledge about impact of siliconate on the composition and formation of the cement phases. Both, the XRD and DTGA/TG analyze showed noticeable changes in portlandite formation during the first days of hydration. The conducted research and obtained results reveal the innovative and novel application of potassium methylsiliconate as retarders, which prolongs the workability of fresh mixture and improves the compressive strength of matured concrete and mortar. This admixtures can be a competitive alternative to traditional retarders.

Organosilicon Compounds in Hot-Melt Adhesive Technologies.

Hot-melt adhesives (HMAs) are thermoplastic materials that can bond various substrates by solidifying rapidly upon cooling from the molten state, and their modification with organosilicon compounds can result in crosslinking behavior, characteristic of gels. Organosilicon compounds are hybrid molecules that have both inorganic and organic components and can enhance the properties and performance of HMAs. The gel aspect of HMA with and without organosilicon modifiers can be considered in organosilicon-modified systems, the modifiers are often either sol-gel condensation products or their mechanism of action on the adherent surface can be considered of sol-gel type. The purpose of this manuscript is to present the current state of the art on the formulation, characterization, and application of HMAs and optimize their performance with organosilicon compounds for application in various industries such as automotive, construction, and photovoltaics. This review covers articles published within the period of 2018-2022. The article is divided into sections, in which information about hot-melt adhesives is described at the beginning. The following part of the presented review focuses on the composition of hot-melt adhesives, which takes into account the use of organosilicon compounds. The last part of this review outlines the future trends in hot-melt adhesives.

Silicones in Cosmetics

The structural diversity of organosilicon compounds used in decorative and care cosmetic products is studied. The unique physicochemical properties of silicones allowing their application as emollients, moisturizers, emulsifiers, film formers, viscosity regulators, and antistatic and binding agents are described. Mechanisms of action of various structure silicones, due to which organosilicon compounds are advantageously used to impart certain properties to cosmetic products, are demonstrated. A comparative analysis of the efficiency of silicones versus natural compounds serving similar functions in cosmetic products is performed. The issue of silicone safety for human health is considered.