Photochemistry of Cyclic Trisilanes: “Spring‐Loaded” Precursors to Methylphenylsilylene

Moiseev, Andrey G.; Coulais, Eugenie; Leigh, William J.

doi:10.1002/chem.200901249

Cited by 9 publications

(9 citation statements)

References 52 publications

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“…Transient silylenes have been characterized using UV–vis and infrared spectroscopy in frozen matrices, and in the gas phase and fluid solution by time-resolved UV–vis spectrophotometry, or flash photolysis. This has allowed the direct detection and characterization of the simplest carbon-substituted silylenes in solution, including SiMe 2 , − , SiPh 2 , − SiMePh, and SiMes 2 (Mes = 2,4,6-trimethylphenyl), using oligosilanes such as 2 – 4 as photoprecursors.…”

Section: Introductionsupporting

confidence: 85%

Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution

Duffy

Leigh

2019

Organometallics

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Di-tert-butylsilylene (Si t Bu 2 ) has been detected directly in solution and its reactivity characterized by laser flash photolysis methods. Laser photolysis of 7,7-di-tert-butyl-7-silabicyclo[4.1.0]heptane (5) affords a transient product that exhibits λ max ≈ 520 nm and decays on the microsecond time scale, concurrent with the growth of a second, much longer-lived species exhibiting λ max = 290, 430 nm. The two species are assigned to di-tert-butylsilylene (Si t Bu 2 ) and its disilene dimer, tetratert-butyldisilene ( t Bu 2 SiSi t Bu 2 , 8), respectively. Transient absorption spectra recorded by laser photolysis of hexa-tert-butylcyclotrisilane ( 7) are consistent with the prompt formation of both Si t Bu 2 and 8, the former appearing as a weak shoulder absorption on the red edge of the intense absorption band due to the disilene. Absolute rate constants were determined for the reactions of Si t Bu 2 with a variety of representative silylene substrates in hexanes at 25 °C, including methanol, triethylsilane, acetic acid, acetone, molecular oxygen, and four aliphatic alkenes (1-hexene, cyclohexene, cis-cyclooctene, and 2,3-dimethyl-2-butene). Rate and(or) equilibrium constants for Lewis acid−base complexation of the silylene with diethyl ether, tetrahydrofuran, tetrahydrothiophene, and diethyl-and triethylamine were also determined, along with the UV−vis absorption spectra of the corresponding Lewis acid−base complexes. Rate constants for the reactions of dimethylsilylene (SiMe 2 ) and dimesitylsilylene (SiMes 2 ) with cis-cyclooctene, 2,3-dimethyl-2-butene, and 1hexene are also reported, enabling a comprehensive assessment to be made of steric effects on the reactivities of simple (transient) dialkyl-and diarylsilylene derivatives in solution. The kinetic data show the reactivity of Si t Bu 2 to be intermediate between that of SiMe 2 and SiMes 2 under similar conditions, with the (2 + 1)-cycloaddition reactions with alkenes exhibiting the largest variations in rate constant as a function of substitution at Si. Absolute rate constants for the reactions of tetra-tertbutyldisilene (8) with O 2 and acetone are also reported.

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Section: Introductionsupporting

confidence: 85%

Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution

Duffy

Leigh

2019

Organometallics

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“…The photochemistry of catenated group 14 compounds is of interest since this method can be used to convert one type of catenate to another and also can be used for the generation of reactive intermediates including silylenes, germylenes, stannylenes, and group 14 element centered radical species that can be trapped and characterized . In the case of germanium, the photochemistry of the cyclotrigermane (Mes 2 Ge) 3 has been the most extensively studied and it has been shown that this compound is photochemically converted to a germylene Mes 2 Ge : and a digermene Mes 2 Ge=GeMes 2 .…”

Section: Introductionmentioning

confidence: 99%

Photodecompostion of the Oligogermanes nBu3GeGePh2GenBu3 and nBu3GeGePh3: Identification of the Photoproducts by Spectroscopic and Spectrometric Methods

et al. 2016

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The oligogermane nBu 3 GeGePh 2 GenBu 3 was photolyzed using UV-C light in the presence of acetic acid as a trapping agent and the photoproducts were identified using 1 H NMR spectroscopy, gas chromatography/electron-impact mass spectrometry, and high resolution accurate mass mass spectrometry. The products identified were the germanes nBu 3 GeH, nBu 3 GeOAc, and Ph 2 Ge(H)OAc (OAc = C 2 H 3 O 2 ) and the diger- [a]

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“…Silylenes are important intermediates in silicon hydride and organosilicon chemistry. − Their characteristic reactions include insertions into Si–H, Si–OR, and O–H bonds and π-type additions across CC and CC bonds. Many of the fine details of the mechanisms of these reactions have been revealed by time-resolved kinetics studies employing direct monitoring of silylenes. − In recent times, much attention has been devoted to the preparation and properties of large silylenes, stabilized either by bulky substituents, or by being built into N-heterocyclic rings or with N-heterocyclic adducts. − Nevertheless there still remains a need to uncover further details of the behavior of the smaller, more reactive silylenes to establish a reactivity baseline.…”

Section: Introductionmentioning

confidence: 99%

Time-Resolved Gas-Phase Kinetic, Quantum Chemical, and RRKM Studies of the Reaction of Silylene with 2,5-Dihydrofuran

et al. 2015

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Time-resolved kinetics studies of silylene, SiH2, generated by laser flash photolysis of phenylsilane, were performed to obtain rate coefficients for its bimolecular reaction with 2,5-dihydrofuran (2,5-DHF). The reaction was studied in the gas phase over the pressure range of 1-100 Torr in SF6 bath gas, at five temperatures in the range of 296-598 K. The reaction showed pressure dependences characteristic of a third body assisted association. The second-order rate coefficients obtained by Rice-Ramsperger-Kassel-Marcus (RRKM)-assisted extrapolation to the high-pressure limit at each temperature fitted the following Arrhenius equation where the error limits are single standard deviations: log(k/cm(3) molecule(-1) s(-1)) = (-9.96 ± 0.08) + (3.38 ± 0.62 kJ mol(-1))/RT ln 10. End-product analysis revealed no GC-identifiable product. Quantum chemical (ab initio) calculations indicate that reaction of SiH2 with 2,5-DHF can occur at both the double bond (to form a silirane) and the O atom (to form a donor-acceptor, zwitterionic complex) via barrierless processes. Further possible reaction steps were explored, of which the only viable one appears to be decomposition of the O-complex to give 1,3-butadiene + silanone, although isomerization of the silirane cannot be completely ruled out. The potential energy surface for SiH2 + 2,5-DHF is consistent with that of SiH2 with Me2O, and with that of SiH2 with cis-but-2-ene, the simplest reference reactions. RRKM calculations incorporating reaction at both π- and O atom sites, can be made to fit the experimental rate coefficient pressure dependence curves at 296-476 K, giving values for k(∞)(π) and k(∞)(O) that indicate the latter is larger in magnitude at all temperatures, in contrast to values from individual model reactions. This unexpected result suggests that, in 2,5-DHF with its two different reaction sites, the O atom exerts the more pronounced electrophilic attraction on the approaching silylene. Arrhenius parameters for the individual pathways were obtained. The lack of a fit at 598 K is consistent with decomposition of the O-complex to give 1,3-butadiene + silanone.

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Photochemistry of Cyclic Trisilanes: “Spring‐Loaded” Precursors to Methylphenylsilylene

Cited by 9 publications

References 52 publications

Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution

Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution

Photodecompostion of the Oligogermanes nBu3GeGePh2GenBu3 and nBu3GeGePh3: Identification of the Photoproducts by Spectroscopic and Spectrometric Methods

Time-Resolved Gas-Phase Kinetic, Quantum Chemical, and RRKM Studies of the Reaction of Silylene with 2,5-Dihydrofuran

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Photochemistry of Cyclic Trisilanes: “Spring‐Loaded” Precursors to Methylphenylsilylene

Cited by 9 publications

References 52 publications

Photochemical Generation and Characterization of Di-tert-butylsilylene (SitBu2) in Solution

Photochemical Generation and Characterization of Di-tert-butylsilylene (SitBu2) in Solution

Photodecompostion of the Oligogermanes nBu3GeGePh2GenBu3 and nBu3GeGePh3: Identification of the Photoproducts by Spectroscopic and Spectrometric Methods

Time-Resolved Gas-Phase Kinetic, Quantum Chemical, and RRKM Studies of the Reaction of Silylene with 2,5-Dihydrofuran

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Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution

Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution