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14 pages, 3454 KB

Open AccessFeature PaperArticle

Synthesis of Star Isotactic Polypropylene via Styryldichlorosilane/Hydrogen Consecutive Chain Transfer Reaction

by Naw Jar, Fengtao Chen and Jin-Yong Dong

Catalysts 2025, 15(4), 331; https://doi.org/10.3390/catal15040331 - 31 Mar 2025

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This paper elucidates the consecutive chain transfer reaction, initially to (p-vinylphenyl) methyl dichlorosilane (or (p-vinylbenzyl) methyl dichlorosilane), followed by hydrogen, during metallocene-catalyzed propylene polymerization by an isospecific metallocene catalyst (i.e., rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride, I)/ activated with methylaluminoxane (MAO), rendering [...] Read more.

This paper elucidates the consecutive chain transfer reaction, initially to (p-vinylphenyl) methyl dichlorosilane (or (p-vinylbenzyl) methyl dichlorosilane), followed by hydrogen, during metallocene-catalyzed propylene polymerization by an isospecific metallocene catalyst (i.e., rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride, I)/ activated with methylaluminoxane (MAO), rendering a catalytic access styryldichlorosilane capped isotactic polypropylenes (iPP). The PP molecular weight is inversely related to the molar ratio of [(p-vinylphenyl) methyl dichlorosilane]/[propylene] and [(p-vinylbenzyl) methyl dichlorosilane]/[propylene]. Every polypropylene chain formed presents a terminal (p-vinylphenyl) methyl dichlorosilane (or (p-vinylbenzyl) methyl dichlorosilane) unit. Hydrogen enhances the concentration of the starting arm polymer for the subsequent synthesis of the star polymer by increasing the incorporation of the chain terminal group. In order to create star polymers with isotactic polypropylene(iPP) as the arm and a siloxane cross-linking structure as the core, the terminal dichlorosilane iPP unit can work up (with water) to create cyclic siloxane oligomer interlinkages between iPP chains. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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16 pages, 3972 KB

Open AccessArticle

Theoretical Investigation of Interconversion Pathways and Intermediates in Hydride/Silyl Exchange of Niobocene Hydride–Silyl Complexes: A DFT Study Incorporating Conformational Search and Interaction Region Indicator (IRI) Analysis

by Dapeng Zhang and Naoki Kishimoto

Molecules 2024, 29(21), 5075; https://doi.org/10.3390/molecules29215075 - 26 Oct 2024

Cited by 2 | Viewed by 1456

Abstract

Niobocene hydride–silyl complexes exhibit intriguing structural characteristics with the potential for direct hydride/silyl exchange, where hydride migration plays a crucial role during conformational interconversion. In this study, quantum chemical calculations were utilized to investigate the transformation pathways involved in hydride/silyl exchange in niobocene [...] Read more.

Niobocene hydride–silyl complexes exhibit intriguing structural characteristics with the potential for direct hydride/silyl exchange, where hydride migration plays a crucial role during conformational interconversion. In this study, quantum chemical calculations were utilized to investigate the transformation pathways involved in hydride/silyl exchange in niobocene trihydride complexes with various dichlorosilanes, including SiCl₂Me₂, SiCl₂ⁱPr₂, and SiCl₂MePh ligands. The conformational changes and hydride shifts within these niobocene hydride–silyl complexes were examined, and key intermediates were identified. Electronic wavefunction analysis provided insights into the coordination configurations and the nature of inter-ligand interactions. Interaction region indicator (IRI) analysis revealed Van der Waals interactions between chloride atoms and cyclopentadienyl rings, as well as between chloride atoms and Me, ⁱPr, and Ph groups. Notably, distinct interactions between hydride ligands, including those from Si-H moieties and coordinated hydrogen atoms, were observed. Both lateral and central conformations, with respect to silicon coordination to the niobium center, were considered. This study enhances the understanding of intermediate conformations in the hydride/silyl exchange process and provides a detailed characterization of inter-ligand interactions, offering valuable insights for analyzing metallocene complexes with organic ligand coordination. Full article

(This article belongs to the Special Issue Featured Papers in Organometallic Chemistry—2nd Edition)

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13 pages, 4060 KB

Open AccessArticle

Promising Catalyst for Chlorosilane Dismutation

by Olesya Zhuchok, Yegor Stolmakov, Alexandra Kalinina, Vitaly Medov, Darya Belousova, Nikita Maleev and Georgy Mochalov

Sci 2024, 6(3), 38; https://doi.org/10.3390/sci6030038 - 1 Jul 2024

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Abstract

Currently, the most common method of silane synthesis for electronics and photovoltaics is trichlorosilane dismutation. Therefore, an experimental study of the kinetics of the dismutation reaction of chlorosilanes is of scientific and practical interest. A catalyst has been proposed that allows the dismutation [...] Read more.

Currently, the most common method of silane synthesis for electronics and photovoltaics is trichlorosilane dismutation. Therefore, an experimental study of the kinetics of the dismutation reaction of chlorosilanes is of scientific and practical interest. A catalyst has been proposed that allows the dismutation reaction to be carried out in a wide range of temperatures and pressures. Both kinetic and thermodynamic data on the dependence of the rate of the dismutation reactions of trichlorosilane, dichlorosilane, and monochlorosilane on pressure were experimentally obtained. In addition, the dependence of saturated vapor pressure on temperature for monochlorosilane and dichlorosilane were also experimentally determined. Using the example of TCS, it was experimentally established that increasing the pressure to six atmospheres makes it possible to increase the specific productivity of the reactor by at least an order of magnitude due to the acceleration of the chemical reaction and the increase in the molar concentration of chlorosilanes in the vapor mixture. Consequently, it becomes possible to multiply the reactor’s load on the substance and, accordingly, the performance of the chlorosilane dismutation apparatus in general. Full article

(This article belongs to the Section Chemistry Science)

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14 pages, 5693 KB

Open AccessArticle

Synthesis and Application of Polymer SXFA in the Detection of Organophosphine Agents with a SAW Sensor

by Cancan Yan, Molin Qin, Tengxiao Guo, Lin Zhang, Junchao Yang and Yong Pan

Polymers 2024, 16(6), 784; https://doi.org/10.3390/polym16060784 - 12 Mar 2024

Cited by 4 | Viewed by 1766

Abstract

The effective detection of isopropyl methylfluorophosphonate (GB, sarin), a type of organophosphine poisoning agent, is an urgent issue to address to maintain public safety. In this research, a gas-sensitive film material, poly (4-hydroxy-4,4-bis trifluoromethyl)-butyl-1-enyl)-siloxane (SXFA), with a structure of hexafluoroisopropyl (HFIP) functional group [...] Read more.

The effective detection of isopropyl methylfluorophosphonate (GB, sarin), a type of organophosphine poisoning agent, is an urgent issue to address to maintain public safety. In this research, a gas-sensitive film material, poly (4-hydroxy-4,4-bis trifluoromethyl)-butyl-1-enyl)-siloxane (SXFA), with a structure of hexafluoroisopropyl (HFIP) functional group was synthesized by using methyl vinylpropyl dichlorosilane and hexafluoroacetone trihydrate as initial materials. The synthesis process products were characterized using FTIR. SXFA was prepared on a 200 MHz shear surface wave delay line using the spin-coating method for GB detection. A detection limit of <0.1 mg/m³ was achieved through conditional experiments. Meanwhile, we also obtained a maximum response of 2.168 mV at a 0.1 mg/m³ concentration, indicating the much lower detection limit of the SAW-SXFA sensor. Additionally, a maximum response standard deviation of 0.11 mV with a coefficient of variation of 0.01 and a maximum recovery standard deviation of 0.22 mV with a coefficient of variation of 0.02 were also obtained through five repeated experiments. The results show that the SAW-SXFA sensor has strong selectivity and reproducibility, good selectivity, positive detection ability, high sensitivity, and fast alarm performance for sarin detection. Full article

(This article belongs to the Special Issue Polymer Materials in Sensors, Actuators and Energy Conversion II)

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17 pages, 3821 KB

Open AccessArticle

Thermodynamics and Kinetics of the Reaction of Catalytic Dismutation of Chlorosilanes in the Vapor Phase in the Temperature Range of 353–393 K

by Georgy Mochalov, Yegor Stolmakov and Olesya Zhuchok

ChemEngineering 2023, 7(1), 13; https://doi.org/10.3390/chemengineering7010013 - 10 Feb 2023

Cited by 4 | Viewed by 3167

Abstract

Currently, the most common method of silane synthesis for electronics and photovoltaics is trichlorosilane (TS) dismutation. TS dismutation proceeds in the form of a reactions cascade, therefore its study is of both practical and scientific interest. The results of calculating the equilibrium composition [...] Read more.

Currently, the most common method of silane synthesis for electronics and photovoltaics is trichlorosilane (TS) dismutation. TS dismutation proceeds in the form of a reactions cascade, therefore its study is of both practical and scientific interest. The results of calculating the equilibrium composition of the reaction mixture in the vapor phase based on literature data from various sources were not reliable. Therefore, the dependence of the composition of the reaction mixture on the time of contact of the TS vapor with the catalyst under static conditions was experimentally investigated. The stationary composition of the mixture, close to equilibrium, was determined. A good agreement of the obtained results with the literature data in one of the sources was shown. The kinetics of the dismutation reaction of TS and dichlorosilane (DCS) was carried out by the flow method. As a result of regression analysis of experimental data, the rate constants of the direct and reverse dismutation reactions of TS, DCS, and monochlorosilane (MSC) were obtained. The rate constants were used to calculate the equilibrium composition of the reaction mixture. A good agreement between the calculated and experimental data was shown. Full article

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13 pages, 22831 KB

Open AccessArticle

Synthesis of 1,1,3,3,5,5-Hexamethyl-7,7-diorganocyclotetrasiloxanes and Its Copolymers

by Evgeniya V. Talalaeva, Aleksandra A. Kalinina, Evgeniy V. Chernov, Alina G. Khmelnitskaia, Marina A. Obrezkova, Georgii V. Cherkaev and Aziz M. Muzafarov

Polymers 2022, 14(1), 28; https://doi.org/10.3390/polym14010028 - 22 Dec 2021

Cited by 2 | Viewed by 3453

Abstract

This paper reports a method for the synthesis of 1,1,3,3,5,5-hexamethyl-7,7-diorganocyclotetrasiloxanes by the interaction of 1,5-disodiumoxyhexamethylsiloxane with dichlorodiorganosilanes such as methyl-, methylvinyl-, methylphenyl-, diphenyl- and diethyl dichlorosilanes. Depending on the reaction conditions, the preparative yield of the target cyclotetrasiloxanes is 55–75%. Along with mixed [...] Read more.

This paper reports a method for the synthesis of 1,1,3,3,5,5-hexamethyl-7,7-diorganocyclotetrasiloxanes by the interaction of 1,5-disodiumoxyhexamethylsiloxane with dichlorodiorganosilanes such as methyl-, methylvinyl-, methylphenyl-, diphenyl- and diethyl dichlorosilanes. Depending on the reaction conditions, the preparative yield of the target cyclotetrasiloxanes is 55–75%. Along with mixed cyclotetrasiloxanes, the proposed method leads to the formation of polymers with regular alternation of diorganosylil and dimethylsylil units. For example, in the case of dichlorodiethylsilane, 70% content of linear poly(diethyl)dimethylsiloxanes with regular alternation of units can be achieved in the reaction product. Using 7,7-diethyl-1,1,3,3,5,5-hexamethylcyclotetrasiloxane as an example, the prospects of the mixed cycle in copolymer preparation in comparison with the copolymerization of octamethyl- and octaethylcyclotetrasiloxanes are shown. Full article

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11 pages, 7116 KB

Open AccessArticle

Epitaxial Growth of Si and SiGe Using High-Order Silanes without a Carrier Gas at Low Temperatures via UHVCVD and LPCVD

by Dae-Seop Byeon, Choonghee Cho, Dongmin Yoon, Yongjoon Choi, Kiseok Lee, Seunghyun Baik and Dae-Hong Ko

Coatings 2021, 11(5), 568; https://doi.org/10.3390/coatings11050568 - 13 May 2021

Cited by 16 | Viewed by 7447

Abstract

Conventional Si or SiGe epitaxy via chemical vapor deposition is performed at high temperatures with a large amount of hydrogen gas using silane (SiH₄) or dichlorosilane (SiCl₂H₂) precursors. These conventional precursors show low growth rates at low [...] Read more.

Conventional Si or SiGe epitaxy via chemical vapor deposition is performed at high temperatures with a large amount of hydrogen gas using silane (SiH₄) or dichlorosilane (SiCl₂H₂) precursors. These conventional precursors show low growth rates at low temperatures, particularly below 500 °C although a low thermal budget becomes more important for modern fabrication techniques. High-order silane precursors, such as disilane, trisilane, and tetrasilane, are candidates for low-temperature epitaxy due to the lower strength of the Si-Si bonds compared to that of the Si-H bonds. In addition, the consumption of vast amounts of hydrogen gas is an additional burden of the low-temperature process due to its low throughput. In this study, we explored Si and SiGe epitaxial growth behaviors using several high-order silanes under ultra-high vacuum chemical vapor deposition (UHVCVD) and low-pressure chemical vapor deposition (LPCVD) conditions without a carrier gas. Disilane showed high-quality epi-growth under both pressure conditions, whereas trisilane and tetrasilane showed enhanced growth rates and lower quality. Full article

(This article belongs to the Section Thin Films)

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8 pages, 1323 KB

Open AccessArticle

Synthesis of a Dichlorodigermasilane: Double Si–Cl Activation by a Ge=Ge Unit

by Tomohiro Sugahara, Norihiro Tokitoh and Takahiro Sasamori

Inorganics 2017, 5(4), 79; https://doi.org/10.3390/inorganics5040079 - 14 Nov 2017

Cited by 7 | Viewed by 4802

Abstract

Halogenated oligosilanes and oligogermanes are interesting compounds in oligosilane chemistry from the viewpoint of silicon-based-materials. Herein, it was demonstrated that a 1,2-digermacyclobutadiene derivative could work as a bis-germylene building block towards double Si–Cl activation to give a halogenated oligometallane, a bis(chlorogermyl)dichlorosilane derivative. Full article

(This article belongs to the Special Issue Coordination Chemistry of Silicon)

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