Silane-induced ring-opening polymerization of 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclopentane catalyzed by a triruthenium cluster

The silane-induced ring-opening polymerization of a cyclic siloxane, 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclopentane (2), is catalyzed by a ruthenium cluster, (μ₃,η²:η³:η⁵-acenapthylene)Ru₃(CO)₇ (1), to give poly(tetramethylsilethylenesiloxane) with M_n=6300–780,000 and M_w/M_n=1.5–3.0. The molecular weight of the polymer can be controlled by changing the concentration of the monomer solution. Addition of acetone results in formation of the polymer with M_n=4400, spectroscopic analysis of which reveals existence of a siloxy and an isopropoxy moieties at the end group.     

Chemistry and polymerization of 1, 1, 3, 3-tetramethyl-1, 3-disila-2-oxaindane

Reaction of o-dichlorobenzene with dimethylmethoxychlorosilane and sodium leads to the isolation of dimethyl(o-chlorophenyl) methoxysilane, o-bis(bimethylmethoxysilyl)benzene, 1,1,3,3-tetramethyl-1,3-disila-2-oxaindane, and 1, 1-dimethyl-1-silarribenzocycloheptatriene. When I is polymerized with H₂SO₄, the phenyl group is observed to split off.     

3D single cyclized polymer chain structure from controlled polymerization of multi-vinyl monomers: beyond Flory-Stockmayer theory

Controlled/living radical polymerization (CRP) is a widely used technique that allows the synthesis of defined polymer architectures through precise control of molecular weights and distributions. However, the architectures of polymers prepared by the CRP techniques are limited to linear, cross-linked, and branched/dendritic structures. Here, we report the preparation of a new 3D single cyclized polymer chain structure from an in situ deactivation enhanced atom transfer radical polymerization of multivinyl monomers (MVMs), which are conventionally used for the production of branched/cross-linked polymeric materials as defined by P. Flory and W. Stockmayer nearly 70 years ago. We provide new evidence to demonstrate that it is possible to kinetically control both the macromolecular architecture and the critical gelling point in the polymerization of MVMs, suggesting the classical Flory-Stockmayer mean field theory should be supplemented with a new kinetic theory based on the space and instantaneous growth boundary concept.     

Preparation of sila-functional 3-sila-1-thiacyclohexanes

First sila-functional heterocycles 7 and 9 with Si and S atoms in 1,3-position bearing the reactive X group at silicon (X = i-PrO, F) were readily prepared from the corresponding phenyl-protected cycle 6 in good yields via Ph-Si bond cleavage by electrophilic reagents. Treatment of i-propoxy derivative 7 with LiAlH₄ gave heterocycle 8 with Si-H bond.     

Electron diffraction study of molecular structure and inversion potential for 1,1-dimethylsilacyclobutane and 1,1,3,3-tetramethyl-1,3-disilacyclobutane

The geometrical parameters for 1,1-dimethylsilacyclobiitane and 1,1,3,3-tetramethyl-13-disilacyclobutune are detemiined by gas phase electron diffraction analysis using a dynamic model, which considers ring inversion as a large-amplitude motion. The structural and potential function parameters were refined with allowance for molecular geometry relaxation estimated by quantum chemical calculations with an HF/6-311G** basis. The potential function of 1,1-dim ethylsilacyclobutane is represented as V(ϕ) = V₀[(ϕ/ϕ_e)² − 1]² with V₀ = 1.3 ± 1.2 kcallmole and ϕ_e = 29.7±4.5°, where ϕ is the ring puckering angle. A more reliable estimate for the height of the barrier (V₀ = 0.56 kcallmole) was obtained by solving the one-dimensional quantum vibrational problem and by fitting the frequency of the 0 →2 transition to the experimental value. For 1,1,3,3-tetram ethyl-1,3-disilacyclobutane, the potential function is adequately represented bx V(ϕ) = Aϕ², where A = (4.9 ± 1.8) · 10⁻⁴ kcall(mole · deg²) with a minimum coiresponding to a planar ring conformation with ϕ = 0°. The calculated structural parameters are compared with the data for related compounds. Translated fromZhumal Struktumoi Khimii. Vol. 41, No. 2, pp. 269–284, March–April, 2000     

Anionic polymerization of 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane

In the first of a two-part series, a study has been made of the anionic polymerization of a five-membered cyclocarbosiloxane, 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane. The polymerization was initiated by lithium n-butyldiphenylsilanolate in the presence of tetrahydrofuran. The chemical shifts of the protons of the cyclic monomer and the polymer were found to be different, and therefore the rate of polymerization was obtained in an NMR spectrometer. The effects of varying the concentrations of THF, initiator, and water upon the rate of polymerization and upon the molecular weight and the molecular weight distribution were investigated. At a constant concentration of monomer and initiator, the rate of polymerization increased when the THF concentration was increased. At a constant concentration of monomer and THF the rate of polymerization reached a constant value when the initiator concentration was varied. The molecular weight and the molecular weight distribution were dependent upon the initiator to water ratio, whereas water concentration had little effect on the rate of polymerization. Essentially monodispersed polymers were obtained when the concentration of initiator was in large excess to that of water or vice versa. A bimodal distribution in molecular weight was obtained when the concentration of initiator was approximately equal to that of water. The apparent activation energy of polymerization was 12.7 kcal/mole.     

The interaction of boron halides with 1,1,3,3-tetramethyl-1,3-disilacyclobutane

The exothermic reaction of BX₃ (X = F, Cl, Br) with 1,1,3,3-tetramethyl-1,3disilacyclobutane (I) gave the ring-cleavage product XMe₂SiCH₂Me₂SiCH₂BX₂ (II) in almost quantitative yield. The order of activity was BBr₃ > BCl₃ > BF₃. Heating compounds of structure II at 180°C for 40 h did not affect IIa (X = F) but caused a complete rearrangement of IIc (X = Br) to BrMe₂SiCiH₂MeBrSiCiH₂BMeBr (IIIc). Compound IIb (X = Cl) was incompletely (65%) converted to ClMe₂SiCH₂MeClSiCH₂BMeCl (IIIb) under the stated conditions. It was concluded that the thermal rearrangement most likely proceeded by an intramolecular mechanism since only one isomer was found.     

Transformations of 1,1,3,3-tetramethyl-1,3-disilacyclobutane in the presence of zirconium tetrachloride

Conclusions One of the possible pathways for the catalytic decomposition of 1,1,3,3-tetramethyl-1,3-disilacyclobutane in the presence of zirconium tetrachloride is the insertion of a dimethylsilaethylene intermediate into the ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1917–1919, August, 1985.The authors express their gratitude to A. I. Mikaya for taking the mass spectra.     

Transformation of 1,1,3,3-tetramethyl-1,3-disilacyclobutane in presence of aluminum chloride

Conclusions The reaction of equimolar amounts of 1,1,3,3-tetramethyl-1,3-disilacyclobutane and aluminum chloride gives tetramethylsilane and a mixture of linear and cyclic silmethylene compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 953–955, April, 1975.     

Structure of 4-sila-3-platinacyclobutene and its formation via Pt-promoted gamma-Si-H bond activation of 3-sila-1-propenylplatinum precursor

4-Sila-3-platinacyclobutene was isolated from the reaction of Pt(SiHPh2)2(PMe3)2 with dimethyl acetylenedicarboxylate (DMAD) and characterized by X-ray crystallography. The formation pathway was found to involve gamma-Si-H bond activation of the 3-sila-1-propenylplatinum intermediate that is formed by the insertion of a DMAD into a Pt-Si bond of Pt(SiHPh2)2(PMe3)2.     

Kinetics of formation of the topological structure during radical polymerization accompanied by the reaction of chain transfer to the polymer

The structural-kinetic features of radical polymerization accompanied by chain transfer to the polymer are considered in this study. The kinetic equations are solved in a general form without any assumptions. The expression for the critical conversion of gel formation (the gel point), α_c, is obtained: $\alpha _c^{ - 1} = 1 + (1 - \delta )[M]_0 (k_{trp} - (k_{trp} )_c )/k_t [R]$ . The resulting α_c values are compared with the data calculated through the monoradical approach, when it was assumed that the steady-state approximation not only for total radical concentration [R] but also for macroradical concentration [R _i ] can be used. A close agreement between the results is demonstrated. This fact means that the latter approach can be used to analyze the kinetics of the process. The main topological characteristics of the polymer are obtained: the molecular-mass distribution and the distribution of macro-molecules over the degrees of branching.     

Thermoanalytical studies of 2,2,6,6-tetramethyl-4-oxy-4-ethynylpiperidin-1-oxyl polymerization

The structure transition temperature, monomer melting point and critical temperatures of polymerization and decomposition of 2,2,6,6-tetramethyl-4-oxy-4-ethynylpiperidin-1-oxyl were determined by means of thermal analysis. Some features of the polymerization of the acetylenic monomer were studied via thermal analysis, and IR and ESR spectroscopy.It was shown that, during non-isothermal temperature increase, the mass loss of the sample associated with the exothermic effect of polymerization occurred at the expense of the monoacetylene sublimation process (42%), a reagent explosion and decomposition of the reaction products formed (15%).

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Zusammenfassung Mittels Thermoanalyse wurde die Strukturumwandlungstemperatur, der Monomerschmelzpunkt und die kritischen Temperaturen für Polymerisierung und Zersetzung von 2,2,6,6-Tetramethyl-4-oxy-4-ethynylpiperidin-1-oxyl bestimmt. Mit Hilfe von Thermo-analyse, IR- und ESR-Spektroskopie wurden einige Eigenschaften der Polymerisierung des Acethylen-Monomers untersucht.Es wurde gezeigt, daß bei einem nichtisothermen Temperaturanstieg der Massenverlust der Probe zunimmt, verbunden mit einem exothermen Effekt der eingetretenen Polymerisierung auf Kosten des Monoacetylen-Sublimierungsprozesses [42%], der Explosion und der Zersetzung der gebildeten Reaktionsprodukte [15%].

     

C3 cyclopolymerization. IV.1 Cationic polymerization of 1,3-bis(4-vinylnaphthyl) propane and the polymer structure yielded

The compound 1,3-bis(4-vinylnaphthyl)propane was prepared by a convenient dehydration of 1,3-bis[4-(1-hydroxyethyl)naphthyl]propane. The structure was confirmed by nuclear magnetic resonance (NMR) spectroscopy. The monomer was polymerized by antimony pentachloride, tin tetrachloride, titanium tetrachloride, or boron trifluoride etherate at 0°C in toluene, 1,2-dichloroethane, or a mixed solvent of 1,2-dichloroethane and nitromethane. Most of runs except for antimony pentachloride–catalyzed ones gave mainly benzene-soluble polymers. The structures of the polymers were studied by several spectroscopic methods. Comparison of NMR and fluorescence spectroscopic data of the polymers with those of syn-and anti-[3.3](1,4)napthalenophane was especially valuable in leading to the conclusion that they were cyclopolymers containing predominantly syn-[3.3]-(1,4)naphthalenophane units in the main chain.     

Synthesis and structure of 3-(hydroxycarbamoyl)-2,2,5,5-tetramethyl-2,5-dihydropyrrol-1-oxyl

Hydroxyamination of 3-chlorocarbonyl-2,2,5,5-tetramethyl-2,5-dihydropyrrol-1-oxyl gave previously unknown 3-(hydroxycarbamoyl)-2,2,5,5-tetramethyl-2,5-dihydropyrrol-1-oxyl whose structure was determined by X-ray analysis. The hydroxamic acid fragment has cis configuration, and the carbonyl group occupies distorted trans position with respect to the double bond in the planar dihydropyrrole ring.