Thermochemical study of 1,1-dimethyl-1-silacyclobutane, 1,1,3,3,-tetramethyl-1,3-disilacyclobutane, and 1,1,3,3,5,5-hexamethyl-1,3,5-trisilacyclohexane

Genchel, V. G.; Demidova, N. V.; Nametkin, N. S.; Gusel’nikov, L. E.; Volnina, É. A.; Burdasov, E. N.; Vdovin, V. M.

doi:10.1007/bf02659543

Cited by 3 publications

(5 citation statements)

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“…It is worthy of note that, for 2b , the calculated value of Δ H 1 (9.6 kcal/mol) is only 1.1 kcal/mol lower than that (10.7 kcal/ mol) found by using the experimental values of Δ H f ( 2 ) = −19.8 kcal/mol and Δ H f ( 3 ) = − 53.9 kcal/mol …”

Section: Resultscontrasting

confidence: 59%

“…f 84.9 ± 6.2, ref . g 26.0, ref ; 25.9 ± 2, ref ; 22 ± 3, ref ; 20.0, ref . h 17.7 ref ; 17.2, ref .…”

Section: Resultsmentioning

confidence: 99%

“…The value of Δ H (2, - 2) (34.9 kcal/mol) was calculated for silacyclobutane at the MRMP/6-311G(d,p)//CASSCF(8,8)/6-31(d)+ZPE level of theory 8a. The enthalpy of reaction 3, Δ H (3, - 3) , was calculated to be 84.9 ± 6.2 kcal/mol 9 using the heats of formation 15.5 kcal/mol 5a and −53.9 kcal/mol, respectively, for 1b and 3b . Calculations of the silene 1a cyclodimerization (reaction −3) enthalpy at the DZ+d CCSD level of theory resulted in the value of −79.1 kcal/mol, but the same calculations at the CASPT2/6-311G**//CASSCF/6-31G* level of theory gave −78.2 kcal/mol 8c…”

Section: Introductionmentioning

confidence: 99%

“…The strain energy is a key parameter when considering the reactivity of the small ring systems. At present, the data on strain energies ( E s , kcal/mol) are restricted by the following silacyclobutanes: (i) parent silacyclobutane 2a , 24.7, 25.8; (ii) 1,1-dimethyl-1-silacyclobutane 2b , 26.0, 25.9 ± 2, 20.0; and (iii) 1,1,3,3-tetramethyl-1,3-disilacyclobutane 3b , 17.7, 17.2…”

Section: Introductionmentioning

confidence: 99%

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Effect of Geminal Substitution at Silicon on 1-Sila- and 1,3-Disilacyclobutanes' Strain Energies, Their 2+2 Cycloreversion Enthalpies, and SiC π-Bond Energies in Silenes

2001

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To evaluate the effect of geminal substitution at silicon on 1-sila- and 1,3-disilacyclobutanes' strain energies, their 2+2 cycloreversion enthalpies, and Si=C pi-bond energies in silenes, an ab initio MO study of silenes, R2Si=CH2 (1), 1-silacyclobutanes, cyclo-R2Si(CH2)3 (2), and 1,3-disilacyclobutanes, cyclo-(R2SiCH2)2 (3), was performed using the level of theory denoted MP4/TZ(d)//MP2/6-31G(d) (TZ means the 6-311G(d) basis set for elements of the second period and hydrogen, and the McLean-Chandler (12s,9p)/[6s,5p](d) basis set for the third period elements). In the series R = H, CH3, SiH3, CH3O, NH2, Cl, F, the growth of the reaction enthalpies and strain energies is proportional to the substituents' electronegativities. 2+2 cycloreversion of 2 is endothermic by 40.6-63.1 kcal/mol, whereas that of 3 is endothermic by 72.7-114.2 kcal/mol. On going from a silicon to a fluorine substituent at the sp2-hybridized silicon atom, the pi-bond energy in 1 weakens by 11.3 kcal/mol, and the Si=C bond length shortens by 0.053 A. The effect of substituents' electronegativities at the double-bonded silicon atom in silenes is formulated as follows: the higher electronegativity, the shorter and the weaker the Si=C pi-bond. The latter is rationalized in terms of more strained geometry resulting from the energetic cost for planarizing the R2SiC moiety. The enthalpies of the ring-opening reaction are 68.0-80.1 kcal/mol (a cleavage of the Si-C bond in 3), 65.0-76.4 kcal/mol (a cleavage of the Si-C bond in 2), and 58.0-64.9 kcal/mol (a cleavage of the C-C bond in 2). The pronounced difference in the enthalpies of 2+2 cycloreversion of 1-sila- and 1,3-disilacyclobutanes is mainly due to the difference in the enthalpies of diradicals' decomposition. The decomposition of diradicals resulting from a cleavage of C-C and Si-C bonds in 2 is exothermic by 24.3-3.3 kcal/mol (apart from the difluoro derivative which is endothermic by 5.1 kcal/mol) and 27.0-13.3 kcal/mol, respectively. The decomposition of a 1,4-diradical resulting from ring opening of 3, apart from the disilyl derivative, is the endothermic process for which the enthalpy varies from 10.6 to 40.4 kcal/mol.

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Section: Resultscontrasting

confidence: 59%

“…f 84.9 ± 6.2, ref . g 26.0, ref ; 25.9 ± 2, ref ; 22 ± 3, ref ; 20.0, ref . h 17.7 ref ; 17.2, ref .…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Geminal Substitution at Silicon on 1-Sila- and 1,3-Disilacyclobutanes' Strain Energies, Their 2+2 Cycloreversion Enthalpies, and SiC π-Bond Energies in Silenes

2001

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“…With the introduction of an additional silicon atom in the four-membered ring, the rings of disilacyclobutane molecules are found to be less puckered than those of monosilacyclobutanes (SCB, MSCB, and DMSCB) . This is reflected in the relatively lower ring strain energy in TMDSCB (74.1 kJ·mol –1 ) than that in DMSCB (108.9 kJ·mol –1 ). The resultant ring stabilization is expected to promote the exocyclic bond rupture.…”

Section: Introductionmentioning

confidence: 97%

Promotion of Exocyclic Bond Cleavages in the Decomposition of 1,3-Disilacyclobutane in the Presence of a Metal Filament

Badran

Shi

2015

J. Phys. Chem. A

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The primary decomposition of 1,3-disilacyclobutane (DSCB) on a tungsten filament and its secondary gas-phase reactions in a hot-wire chemical vapor deposition (CVD) reactor have been studied using laser ionization mass spectrometry. Under the collision-free conditions, DSCB decomposes on the W filament to produce H2 molecules with an activation energy of 43.6 ± 4.1 kJ·mol(-1). With the help of the isotope labeling and chemical trapping methods, the mechanistic details in the secondary gas-phase reactions important in the hot-wire CVD reactor setup have been examined. The dominant pathway has been demonstrated to be the insertion of the cyclic 1,3-disilacyclobut-1-ylidene, generated by exocyclic Si-H bond rupture, into the Si-H bond in DSCB to form 1,1'-bis(1,3-disilacyclobutane) (174 amu). The successful trapping of 1,3-disilacyclobut-1-ylidene by both 1,3-butadiene and trimethylsilane provides compelling evidence for the existence of this cyclic silylene species in the hot-wire CVD reactor with DSCB. Other reactions operating in the reactor include the DSCB cycloreversion to form silene and the ring opening of DSCB via 1,2-H shift to produce silene/methylsilylene and 1-methylsilene/silylene. The introduction of an additional Si atom in the four-membered ring monosilacyclobutane molecule has caused two major changes in the reaction chemistry assumed by DSCB: (1) The endocyclic cycloreversion reactions that dominate in the decomposition of monosilacyclobutane molecules only play a much less important role in the dissociation of DSCB; and (2) the exocyclic bond cleavages are promoted in DSCB due to the ring stabilization caused by the introduction of one additional Si atom.

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Modeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane

Loffhagen

Becker

Czerny

et al. 2020

Plasma Chem Plasma Process

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A time-dependent, spatially one-dimensional fluid-Poisson model is applied to analyze the impact of small amounts of tetramethylsilane (TMS) as precursor on the discharge characteristics of an atmospheric-pressure dielectric barrier discharge (DBD) in argon. Based on an established reaction kinetics for argon, it includes a plasma chemistry for TMS, which is validated by measurements of the ignition voltage at the frequency $$f =86.2\, {\hbox{kHz}}$$ f = 86.2 kHz for TMS amounts of up to 200 ppm. Details of both a reduced Ar-TMS reaction kinetics scheme and an extended plasma-chemistry model involving about 60 species and 580 reactions related to TMS are given. It is found that good agreement between measured and calculated data can be obtained, when assuming that 25% of the reactions of TMS with excited argon atoms with a rate coefficient of $$3.0 \times 10^{-16}\, {\hbox{m}^3/\hbox{s}}$$ 3.0 × 10 - 16 m 3 / s lead to the production of electrons due to Penning ionization. Modeling results for an applied voltage $${U}_{{\mathrm{a}},0} = 4\, {\hbox{kV}}$$ U a , 0 = 4 kV show that TMS is depleted during the residence time of the plasma in the DBD, where the percentage consumption of TMS decreases with increasing TMS fraction because only a finite number of excited argon species is available to dissociate and/or ionize the precursor via energy transfer. Main species resulting from that TMS depletion are presented and discussed. In particular, the analysis clearly indicates that trimethylsilyl cations can be considered to be mainly responsible for the film formation.

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Thermochemical study of 1,1-dimethyl-1-silacyclobutane, 1,1,3,3,-tetramethyl-1,3-disilacyclobutane, and 1,1,3,3,5,5-hexamethyl-1,3,5-trisilacyclohexane

Cited by 3 publications

References 1 publication

Effect of Geminal Substitution at Silicon on 1-Sila- and 1,3-Disilacyclobutanes' Strain Energies, Their 2+2 Cycloreversion Enthalpies, and SiC π-Bond Energies in Silenes

Effect of Geminal Substitution at Silicon on 1-Sila- and 1,3-Disilacyclobutanes' Strain Energies, Their 2+2 Cycloreversion Enthalpies, and SiC π-Bond Energies in Silenes

Promotion of Exocyclic Bond Cleavages in the Decomposition of 1,3-Disilacyclobutane in the Presence of a Metal Filament

Modeling of Atmospheric-Pressure Dielectric Barrier Discharges in Argon with Small Admixtures of Tetramethylsilane

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