Lewis base adducts to diorganosilylenes

Gillette, Gregory R.; Noren, George H.; West, Robert A.

doi:10.1021/om00104a033

Cited by 80 publications

(44 citation statements)

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“…By analogy with findings for SiH 2 +H 2 O [5,6] which has a similar reaction mechanism (and calculated potential energy surface) this suggests that the H 2 Si··NH 3 adduct will be the effective final product under experimental conditions (short timescale/moderate temperatures) because the rearrangement barrier for H 2 Si··NH 3 to H 3 SiNH 2 is too high. Stable donor acceptor adducts of silylenes with N-type lone pair donors have been detected in low temperature matrices [22,23]. The expectation here is therefore of an association reaction, which should require third body assistance to stabilise the initially formed vibrationally excited adduct.…”

Section: Introductionmentioning

confidence: 85%

The reaction between silylene and ammonia: Some gas-phase kinetic and quantum chemical studies

2006

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Time-resolved kinetic studies of the reaction of silylene, SiH 2 , generated by 193 nm laser flash photolysis of silacyclopent-3-ene, have been carried out in the presence of ammonia, NH 3 . Second order kinetics were observed. The reaction was studied in the gas phase at 10 Torr total pressure in SF 6 bath gas at each of the three temperatures, 299, 340 and 400 K. The second order rate constants (laser pulse energy of 60 mJ/pulse) fitted the Arrhenius equation:Experiments at other pressures showed that these rate constants were unaffected by pressure in the range 10-100 Torr, but showed small decreases in value at 3 and 1 Torr. There was also a weak intensity dependence, with rate constants decreasing at laser pulse energies of 30 mJ/pulse. Ab initio calculations at the G3 level of theory, show that SiH 2 +NH 3 should form an initial adduct (donor-acceptor complex), but that energy barriers are too great for further reaction of the adduct. This implies that SiH 2 +NH 3 should be a pressure dependent association reaction. The experimental data are inconsistent with this and we conclude that SiH 2 decays are better explained by reaction of SiH 2 with the amino radical, NH 2 , formed by photodissociation of NH 3 at 193 nm. The mechanism of this previously unstudied reaction is discussed.

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Section: Introductionmentioning

confidence: 85%

The reaction between silylene and ammonia: Some gas-phase kinetic and quantum chemical studies

2006

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“…It has been previously reported that, upon a thermal treatment carried out at T around 200°C or below, both hexaethoxydisilane and hexamethoxydisilane could form reactive species called silylenes (Scheme 3, 5) [36]. These molecules are unstable and highly reactive [37]. On one hand, it has been demonstrated that they rapidly react by insertion with Si-O bonds and produce trisilane structures (Scheme 4, 6) [38].…”

Section: Mechanisms Behind the Materials Synthesesmentioning

confidence: 99%

Synthesis of sol–gel SiO2-based materials using alkoxydisilane precursors: mechanisms and luminescence studies

Fernández‐Sánchez

Rodríguez

Domı́nguez

2014

J Sol-Gel Sci Technol

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This work reports on the mechanisms behind the sol-gel synthesis and versatile luminescent behavior of sol-gel silica-based materials based on hexamethoxydisilane (Hexamet) or hexaethoxydisilane (Hexaet) innocuous monomers, at different annealing temperatures. The resulting as-synthesized materials exhibit an intense photoluminescence (PL) band in the blue region of the spectrum, whose maximum shifted in the region of 430-650 nm by applying an annealing process at different temperatures in the range of 350-1,000°C. This behavior could be attributed to the presence of different silica matrix defect-related luminescent mechanisms. PL emission bands of the Hexamet-derived materials prepared at higher T up to 1,300°C slightly shifted and appeared in the region of 400-700 nm. However, those Hexaet-derived materials annealed at T between 1,000-1,150°C showed bands peaking at and above 800 nm, these being related to a quantum confinement effect induced by the presence of silicon nanocrystals (Si_nc) within the polymer matrix. Based on studies carried out by different microscopy and chemical analysis techniques, the origin of the PL behavior was attributed to the kinetics of the hydrolysis and condensation reactions being different for each monomer, which generate different intermediates and eventual structures during the annealing process. The superior tunable luminescent performance of these environmentallyfriendly materials provides them with the potential for the fabrication of silicon-based light sources.

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“…84 The trapping of silylene (i -Pr 3 Si)(t-Bu 3 Si)Si • •, generated by photolysis of the silirene precursor, with Me 3 SiH resulted in the formation of the intermolecular Si-H insertion product (i -Pr 3 Si)(t-Bu 3 Si)Si(H)SiMe 3 along with the intramolecular C-H insertion byproduct (Scheme 4.25). 84 The trapping of silylene (i -Pr 3 Si)(t-Bu 3 Si)Si • •, generated by photolysis of the silirene precursor, with Me 3 SiH resulted in the formation of the intermolecular Si-H insertion product (i -Pr 3 Si)(t-Bu 3 Si)Si(H)SiMe 3 along with the intramolecular C-H insertion byproduct (Scheme 4.25).…”

Section: Insertion Into Single Bondsmentioning

confidence: 99%

Heavy Analogs of Carbenes: Silylenes, Germylenes, Stannylenes and Plumbylenes

Lee

Sekiguchi

2010

Organometallic Compounds of Low‐Coordinate Si, Ge, Sn and Pb

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The Si-Si bonds of the oligo-or polysilanes chains can be cleaved upon photolysis in two ways, forming either silylenes or silyl radicals. 2 Thus, photolysis of both poly(di-nbutylsilane) and poly(di-n-hexylsilane) with shorter wavelength light [248 nm (pulsed) or 254 nm (CW)] resulted in both extrusion of silylenes R 2 Si • • (R = n-butyl or n-hexyl) trapped with Et 3 SiH and homolytic Si-Si bond cleavage, whereas only polysilyl radicals were observed upon irradiation with longer wavelength light (λ > 300 nm). 3 Among the most frequently used precursors for the photochemical generation of silylenes are trisilanes RR Si(SiMe 3 ) 2 , which readily eliminate hexamethyldisilane Me 3 Si-SiMe 3 to form the corresponding silylenes RR Si • •. Thus, diphenylsilylene Ph 2 Si • • was produced by irradiation of Ph 2 Si(SiMe 3 ) 2 along with the by-products formed from the isomeric silatriene (Scheme 4.1). 4

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Lewis base adducts to diorganosilylenes

Cited by 80 publications

References 0 publications

The reaction between silylene and ammonia: Some gas-phase kinetic and quantum chemical studies

The reaction between silylene and ammonia: Some gas-phase kinetic and quantum chemical studies

Synthesis of sol–gel SiO2-based materials using alkoxydisilane precursors: mechanisms and luminescence studies

Heavy Analogs of Carbenes: Silylenes, Germylenes, Stannylenes and Plumbylenes

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