Hydride Silane Research Articles

Aerobic Co-/ N-Hydroxysuccinimide-Catalyzed Oxidation of p-Tolylsiloxanes to p-Carboxyphenylsiloxanes: Synthesis of Functionalized Siloxanes as Promising Building Blocks for Siloxane-Based Materials.

Synthesis of organosilicon products with a "polar" functional group within organic substituents is one of the most fundamentally and practically important challenges in today's chemistry of silicones. In our study, we suggest a solution to this problem, viz., a high-efficiency preparative method based on aerobic Co-/ N-hydroxysuccinimide (NHSI) catalyzed oxidation of p-tolylsiloxanes to p-carboxyphenylsiloxanes. This approach is based on "green", commercially available, simple, and inexpensive reagents and employs mild reaction conditions: Co(OAc)2/NHSI catalytic system, O2 as the oxidant, process temperature from 40 to 60 °C, atmospheric pressure. This reaction is general and allows for synthesizing both mono- and di-, tri-, and poly( p-carboxyphenyl)siloxanes with p-carboxyphenyl groups at 1,1-, 1,3-, 1,5-, and 1,1,1-positions. All the products were obtained and isolated in gram amounts (up to 5 g) and in high yields (80-96%) and characterized by NMR, ESI-HRMS, GPC, IR, and X-ray data: p-carboxyphenylsiloxanes in crystalline state form HOF-like structures. Furthermore, it was shown that the suggested method is applicable for the oxidation of organic alkylarene derivatives (Ar-CH3, Ar-CH2-R) to the corresponding acids and ketones (Ar-C(O)OH and Ar-C(O)-R), as well as hydride silanes ([Si]-H) to silanols ([Si]-OH). The possibility of synthesizing monomeric (methyl) and polymeric (siloxane-containing PET analogue, Sila-PET) esters based on 1,3-bis( p-carboxyphenyl)disiloxane was studied. These processes occur with retention of the organosiloxane frame and allow to obtain the corresponding products in 90 and 99% yields.

An Yttrium Hydride–Silane Complex as a Structural Model for a σ‐Bond Metathesis Transition State

Ein Strukturmodell für den Übergangszustand der σ-Bindungsmetathese zwischen Si-H- und M-E-Bindungen (M: d0-Übergangsmetall) wurde in Form eines Yttriumhydrid-Silan-Komplexes erhalten (siehe Bild). Die Silan-Einheit verbleibt entweder im Komplex oder wird in Reaktionen des Komplexes mit anderen Substraten freigesetzt.

An Yttrium Hydride–Silane Complex as a Structural Model for a σ‐Bond Metathesis Transition State

A structural model for the transition state of the σ-bond metathesis between SiH and ME bonds (M: d0 transition metal) was obtained through the formation of an yttrium hydride–silane complex (see picture). The silane moiety can be either retained or released during the reactions of the complex with other substrates.

Synthesis and UV curing kinetics of rapidly UV‐curable hyperbranched polycarbosiloxanes

AbstractHyperbranched polycarbosiloxanes with peripheral photo‐crosslinkable groups were synthesized through controllable hydrosilylation reaction from A2‐type and CB3‐type monomers. The polymerization of the monomer pairs was monitored using Fourier transform infrared spectroscopy, from which it was found that vinyl silane and methacrylate groups reacted with hydride silane from the beginning of the reaction. The results thus suggest a step‐by‐step polymerization rather than a two‐step process for this system. The polycarbosiloxanes could be cured rapidly in either nitrogen or air atmosphere, this feature making them attractive for potential application as precursors of advanced ceramic devices with complex structures. The effects of light intensity, reaction temperature and atmosphere on the UV curing rate (Rp) and conversion (α) of the photo‐crosslinkable groups were characterized carefully, and the curing kinetics was also investigated systematically. The results show that Rp and α increased with an increase of light intensity or temperature, and that the inhibiting effect of oxygen in air could be suppressed by enhancing the irradiation intensity. Copyright © 2010 Society of Chemical Industry

Synthesis, characterization and UV curing kinetics of hyperbranched polysiloxysilanes from A2 and CB2 type monomers

A controllable approach to synthesize UV curable hyperbranched polysiloxysilanes from A2 (1,1,3,3-tetramethyldisiloxane) and CB2 type monomers (methyl(vinyl)silanediylbis(oxy)bis(ethane-2,1-diyl) diacrylate and methyl(vinyl) silanediylbis(oxy)bis(ethane-2,1-diyl)bis(2-methylacrylate)) was developed in the presented paper. The polymerization was monitored using FTIR, where a two-step polyaddition mode was observed. Vinyl silane group preferentially reacted with hydride silane, resulting in the formation of AB2 type intermediates containing one hydride silane and two acrylate (or methacrylate) groups, at the same time, there may be low quantity of B4 type intermediates. The intermediates further polymerized to form hyperbranched polymers. The UV curing kinetics of the hyperbranched polymers, especially the effects of atmosphere, content of photoinitiator and light intensity on UV curing behavior were studied in detail. The results indicated that the hyperbranched polymers could be cured rapidly under UV irradiation. The curing rates increased with the enhancement of light intensity, and the inhibition effect of oxygen could be restrained by increasing light intensity.

Diphilic carbosilane dendrimers with different densities of the hydrophilic layer

A universal method for the synthesis of hydrophilic dendrimers was considered. The method is based on a combination of carbosilane dendrimers with different molecular organizations and hydrophilizing agents, viz., substituted hydride silanes containing one and three protected hydroxyl groups. The combination of a limited set of the mentioned reagents makes it possible to control the ratio of hydrophilic and hydrophobic moieties of the molecular structure in wide limits. A simple and convenient method for the removal of trimethylsilyl protection of hydroxyl groups in the surface layer of dendrimers was developed.

Study of Curing Processes in PDMS at Various Stoichiometric Ratios by Longitudinal Ultrasonic Waves

ABSTRACTCuring reactions of linear vinyl terminated poly(dimethylsiloxane) with a four functional hydride silane crosslinker at various stoichiometric ratios, were studied by wave propagation at ultrasonic frequencies. Longitudinal wave velocity was found to be sensitive to the covalent endlinking, and gel point in these systems.The observed changes in longitudinal wave velocity during the reaction are governed by changes in the bulk modulus of the system.

Reactions of hydride silanes with substituted acetylenes in presence of iron carbonyls

1. The reaction of diethylmethylsilane with 1-pentyne in presence of iron pentacarbonyl leads to a complex mixture of diethylmethylpentenylsilanes and diethylmethylpentynylsilanes. Simultaneously, part of the pentyne taken is hydrogenated with formation of pentenes and pentane. 2. Diethylmethylsilane adds to diphenylacetylene in presence of iron pentacarbonyl or diiron nona-carbonyl with close to quantiative yield of the adduct. The reaction goes stereospecifically as a cis addition, and it is not complicated by the hydrogenation of the diphenylacetylene. It is concluded that the hydrogenation of the original unsaturated compound is dependent on the dehydrogenation of the intermediate product of the addition of the silyl group to the unsaturated compound. 3. On the basis of the behavior of cis- and trans-diethylmethyl-1-pentenylsilanes, taken as an example, It was shown that under the conditions of the reaction studied isomerization with migration of the double bond along the molecular chain does not occur.

Synthesis of ?-organosilyl derivatives of propylphosphonic bichloride and diethyl ester

1. The addition of hydride silanes to allylphosphonic dichloride and diethyl ester in presence of chlorplatinic acid or t-butyl peroxide proceeds in accordance with Farmer's rule. 2. It was shown to be possible to prepare 3-(alkylethoxysilyl)propylphosphonic ethyl esters by the Arbuzov reaction in yields of 45–80%.

New method for the preparation of of organosilicon monomers by the high-temperature condensation of alkenyl chlorides, aryl chlorides, and olefins with silanes containing silicon-attached hydrogen

1. The high-temperature condensation (600–700°) of alkenyl and aryl chlorides with hydride silanes (i.e., silanes containing silicon-attached hydrogen) in a flow system at atmospheric pressure is a general method for the synthesis of alkenyl- and aryl-chlorosilanes. On the basis of this new method we developed syntheses, differing from those known previously in their simplicity and high yields, for various organosilicon monomers. 2. A reaction scheme is proposed for the high-temperature condensation of hydride silanes with alkenyl and aryl chlorides; the scheme requires the participation of free radicals. 3. A new reaction of hydride silanes with olefins leading to the formation of alkenylchlorosilanes was discovered.