Abstract:Low-temperature photolysis of tris(trimethylsilyl)silane derivatives in a 3-methylpentane glass at 77 K yields hexamethyldisilane and trimethylsilyl-substituted silylenes. These silylenes exhibit broad n ~ p absorptions at wavelengths typically > 600 nm in the UV and have been captured by 2,3-dimethylbutadiene in cyclohexane at room temperature. Exceptions to the usual position of Ama x have been observed and are discussed.
“…The major constituent of the photolysis products of dioxasilirane 5f was identified as silaester 7f. The intense absorption at 963 cm -1 (calculated: 953 cm -1 ) shows an isotopic shift of -24.6 cm -1 (calculated: -25 cm -1 ) in 18 O 2 -7f and is assigned to the Si-O(Ph) stretching vibration. Two other strong absorptions at 1250 and 1244 cm -1 with pronounced 18 O-isotopic shifts of -26.2 and -44.2 cm -1 are assigned to the C-O and the SidO stretching vibration of 7f, respectively (Table 3).…”
Section: Resultsmentioning
confidence: 95%
“…The limited number of experimental studies on the oxygenation of silylenes is mainly due to the lack of suitable precursors. 16 The photolysis of matrix-isolated trisilanes 10,[17][18][19] produces silylenes in close proximity to disilenes or other products of the precursor decomposition rather than matrixisolated silylenes. Gas-phase thermolysis of disilanes and other thermal precursors [20][21][22] requires very high temperatures, and the photolysis of diazidosilanes 23,24 short-wavelength UV irradiation.…”
The oxidation of methyl(phenyl)silylene, 3f, with molecular oxygen is investigated using matrix isolation spectroscopy in combination with DFT calculations. The UV irradiation (λ > 305 nm) of phenylsilyldiazomethane, 8, matrix-isolated in argon at 10 K, produces silylene 3f in very high yield. In O 2 doped argon matrixes, the thermal reaction of 3f with O 2 could be directly monitored by IR spectroscopy. The only reaction product is dioxasilirane 5f, presumably formed via cyclization of silanone O-oxide 4f. DFT calculations reveal that the activation barrier for the 4f f 5f cyclization is less than 1 kcal/mol, too small to allow the matrix isolation of 4f. Dioxasilirane 5f is photolabile, and irradiation with blue light (λ > 420 nm) results in a [1,2]-phenyl migration to give silaester 7f. The product of the methyl migration, silaester 13, is formed as a minor constituent.
“…The major constituent of the photolysis products of dioxasilirane 5f was identified as silaester 7f. The intense absorption at 963 cm -1 (calculated: 953 cm -1 ) shows an isotopic shift of -24.6 cm -1 (calculated: -25 cm -1 ) in 18 O 2 -7f and is assigned to the Si-O(Ph) stretching vibration. Two other strong absorptions at 1250 and 1244 cm -1 with pronounced 18 O-isotopic shifts of -26.2 and -44.2 cm -1 are assigned to the C-O and the SidO stretching vibration of 7f, respectively (Table 3).…”
Section: Resultsmentioning
confidence: 95%
“…The limited number of experimental studies on the oxygenation of silylenes is mainly due to the lack of suitable precursors. 16 The photolysis of matrix-isolated trisilanes 10,[17][18][19] produces silylenes in close proximity to disilenes or other products of the precursor decomposition rather than matrixisolated silylenes. Gas-phase thermolysis of disilanes and other thermal precursors [20][21][22] requires very high temperatures, and the photolysis of diazidosilanes 23,24 short-wavelength UV irradiation.…”
The oxidation of methyl(phenyl)silylene, 3f, with molecular oxygen is investigated using matrix isolation spectroscopy in combination with DFT calculations. The UV irradiation (λ > 305 nm) of phenylsilyldiazomethane, 8, matrix-isolated in argon at 10 K, produces silylene 3f in very high yield. In O 2 doped argon matrixes, the thermal reaction of 3f with O 2 could be directly monitored by IR spectroscopy. The only reaction product is dioxasilirane 5f, presumably formed via cyclization of silanone O-oxide 4f. DFT calculations reveal that the activation barrier for the 4f f 5f cyclization is less than 1 kcal/mol, too small to allow the matrix isolation of 4f. Dioxasilirane 5f is photolabile, and irradiation with blue light (λ > 420 nm) results in a [1,2]-phenyl migration to give silaester 7f. The product of the methyl migration, silaester 13, is formed as a minor constituent.
“…In terms of the previous discussion, this both raises the energy of the p-orbital and lowers the energy of the n-orbital, hence increasing the HOMO−LUMO gap. A similar argument has been deployed to account for the spectral changes in a series of (trimethylsily)(aryl)silylenes. , 4 Configurational changes in diarylgermylenes induced by bulky tert- butyl substituents.…”
Bis(2,4,6-tri-tert-butylphenyl)germylene
(1), which had been reported to undergo an
insertion of the germanium atom into a C−H bond of an
o-tert-butyl group at room
temperature, was found to be quite stable. Such a C−H insertion
does occur in solution,
forming germaindane 2, but only in the presence of a Lewis
acid such as the starting material
GeCl2. 1 can be stored unchanged at −30
°C for months; at 20 °C it decomposes within
several weeks under release of 1,3,5-tri-tert-butylbenzene.
Compound 1 was characterized
by X-ray diffraction methods. The X-ray structure of 1
shows that the two aryl ligands
have very different geometries: one aryl group is greatly distorted
to give a “boat” form and
the Ge atom is remote from any of the ring planes, while the second
aryl group is only slightly
deformed and the Ge atom lies in the ring plane. UV/vis spectra
exhibit an intense absorption
at 430 nm in solution and at 405 nm in the solid state, which
represents an enormous
hypsochromic shift compared to other germylenes with bulky aryl
ligands. Oxidation of 1
with trimethylamine N-oxide leads to a germanone, which
rearranges very rapidly by a C−H
insertion process yielding the germaindanol 3.
“…Indium monochloride has been shown to add to H 2 or HCl when trapped with these molecules in an argon matrix and photo-activated with broad-band UV irradiation. 32 The products of the reactions are identified, on the basis of 1 H/ 2 H and 35 Cl/ 37 Cl isotopic shifts in the IR spectrum and of density functional calculations, as the discrete hydrides HInCl 2 and H 2 InCl. All six vibrational fundamentals of H 2 InCl and five of the six fundamentals of HInCl 2 have been identified.…”
Section: Main Group Compoundsmentioning
confidence: 99%
“…The position of l max for a range of trimethylsilyl-substituted silylenes trapped in 3-methylpentane glasses at 77 K has been measured. 37 The silylenes are generated by photolysis of tris(trimethylsilyl)silane derivatives and they all exhibit broad n?p absorptions at wavelengths typically above 600 nm. The photochemistry and photooxidation of three acylsilanes (formyltrimethylsilane, acetyltrimethylsilane and benzoyltrimethylsilane) have been studied in argon and O 2 -doped argon matrices.…”
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