Kinetic spectroscopy of diphenylgermylene Ph2Ge following laser flash photolysis of bis(trimethylsilyl) diphenylgermane (Me3Si)2GePh2

Konieczny, S.; Jacobs, S.Joshua; Wilking, Janet K. Braddock; Gaspar, Peter P.

doi:10.1016/0022-328x(88)89115-0

Cited by 31 publications

(33 citation statements)

References 13 publications

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“…Addition of up to 10 mmol/L 2,3-dimethyl-1,3-butadiene (DMB) to hexane solutions of 5f had little effect on the intensity or lifetime of the 450 nm signal due to silene 6f, as expected considering the reported rate constants for reaction of the long-lived transients from 5d and 5e (i.e., silenes 6d and 6e) with this diene, which are in the range of ca. 10 5 (mol/L) -1 s -1 in cyclohexane (31,33). Addition of larger quantities of the diene (30-40 mmol/L) led to corresponding reductions in the intensity of the silene absorption due to screening of the excitation light by the added substrate, and very modest increases in the pseudo first order decay rate constant.…”

Section: Resultsmentioning

confidence: 96%

“…Our flash photolysis results for 5d-5f are indeed consistent with the formation of two distinct transient products in all three cases. The dominant transient absorptions, which we assign to the silenes 6d-6f based on comparisons of their absorption spectra and reactivities to those of the related an- alogues 6a-6c (vide supra), are centered in the 440-460 nm spectral range and exhibit lifetimes of several hundred microseconds or greater; these are the species that were characterized in the earlier laser photolysis studies of 5d (31,32) and 5e (33) in cyclohexane solution. Superimposed on these absorptions in hexane are those assignable to the corresponding silylenes, which are considerably shorter-lived and are quenched several orders of magnitude more rapidly than the 440-460 nm species by MeOH and Et 3 SiH; in all three cases, the rate constants are close to the diffusion-controlled limit and are in good agreement with the values reported by us earlier for the reactions of SiMe 2 and SiPh 2 with the same substrates under similar conditions (34,45).…”

Section: Discussionmentioning

confidence: 98%

“…40% (18,(23)(24)(25)(26)(27)(28)(29)(30). Gaspar and co-workers employed 5d and 5e as precursors to SiMePh (31,32) and SiPh 2 (33), respectively, in some of the earliest reported attempts to study reactive silylenes in solution by laser flash photolysis methods. They described strongly absorbing, long-lived transient species that they assigned (with some reservation) to the corresponding silylenes (31)(32)(33); however, as we have recently shown in the case of 5e (34), it is more likely that the species they characterized in their experiments are in fact the corresponding 1-silahexatriene derivatives and not the silylenes of interest.…”

Section: Introductionmentioning

confidence: 99%

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Substituent effects on silene reactivity — Reactive silenes from photolysis of phenylated tri- and tetrasilanes

Leigh¹,

Moiseev²,

Coulais³

et al. 2008

Can. J. Chem.

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Laser flash photolysis of 2-phenylheptamethyltrisilane (5d), 2,2-diphenylhexamethyltrisilane (5e), and phenyltris(trimethylsilyl)silane (5f) in hexane and acetonitrile solution affords strong, long-lived transient absorptions centered in the 440–470 nm range, which are assigned to the transient silenes formed via [1,3]-trimethylsilyl migration into the ortho-position of a phenyl ring on the basis of their UV–vis spectra and kinetic data for their reactions with methanol (MeOH), acetic acid (AcOH), acetone, 2,3-dimethyl-1,3-butadiene (DMB), carbon tetrachloride (CCl4), and oxygen. The silene derivatives are formed along with the corresponding silylenes (SiMePh, SiPh2, and Si(SiMe3)Ph, respectively) upon photolysis of these compounds in solution, and indeed, weak, short-lived transient absorptions assignable to the silylenes can also be detected in laser photolysis experiments with the three compounds in hexane, superimposed on the much more prominent absorptions due to the silenes. The silylene absorptions are quenched by MeOH and triethylsilane (Et3SiH) with absolute rate constants varying over the narrow ranges of (1.1–1.8) × 1010 (mol/L)–1 s–1 and (2.5–3.6) × 109 (mol/L)–1 s–1, respectively, in excellent agreement with previously reported values for SiPh2 and SiMe2 under the same conditions. The kinetic data obtained for the silenes are compared to previously reported data for the reactions of the same substrates with the related silenes (6a–6c) formed by photolysis of pentamethylphenyl-, 1,1,1,2-tetramethyl-2,2-diphenyl-, and 1,1,1-trimethyl-2,2,2-triphenyldisilane (5a–5c, respectively) under similar conditions. The comparison provides the first systematic, quantitative assessment of the stabilizing effects of trialkylsilyl substitution at the silenic silicon atom in silene derivatives.Key words: silene, silylene, trisilane, tetrasilane, kinetics.

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Section: Resultsmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Substituent effects on silene reactivity — Reactive silenes from photolysis of phenylated tri- and tetrasilanes

Leigh¹,

Moiseev²,

Coulais³

et al. 2008

Can. J. Chem.

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“…A time-resolved study of the reactivity of dimesitylsilylene in hydrocarbon solvents has also been reported [13]. Flash photolysis studies of the reactivity of methylphenyl-and diphenylsilylene (SiMePh and SiPh 2 , respectively) in solution had been reported somewhat earlier by Gaspar and coworkers [14][15][16], but several of the reported rate constants are so significantly different from those determined later for SiMe 2 and SiMes 2 with similar substrates that the basic assignments must be considered questionable [1]. The only comprehensive study of the UV-vis absorption spectra of transient aryl-and alkylsilylenes is that of Michalczyk et al, who reported the spectra of 22 simple silylenes in hydrocarbon matrices at 77 K [17].…”

Section: Introductionmentioning

confidence: 93%

“…The only comprehensive study of the UV-vis absorption spectra of transient aryl-and alkylsilylenes is that of Michalczyk et al, who reported the spectra of 22 simple silylenes in hydrocarbon matrices at 77 K [17]. The arylsilylenes studied in that work were all generated by photolysis of aryltrisilanes, analogous to the precursors employed by Gaspar and coworkers in their studies of SiMePh and SiPh 2 [14][15][16]. In fluid solution, compounds of this type are known to afford significant amounts of transient silenes, derived from 1,3-SiMe 3 migration into the ortho-position of a phenyl ring, in addition to the corresponding silylene [18][19][20].…”

Section: Introductionmentioning

confidence: 97%

The photochemistry of a potential diphenylsilylene precursor. Time-resolved spectroscopic studies of the reactivity of a transient vinylsilirane

et al. 2006

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The photochemistry of 3,4-dimethyl-1,1-diphenylsilacyclopent-3-ene (2), a potential precursor to diphenylsilylene (SiPh 2 ), has been studied in hydrocarbon and methanol solution by steady state and laser flash photolysis techniques. The results are consistent with the formation of three major photoproducts: SiPh 2 (ca. 20%), 2,3-dimethyl-1,3-butadiene (DMB; ca. 20%), and 2-methyl-2-(1-methylethenyl)-1,1-diphenylsilirane (9; ca. 75%), the product of formal photochemical (1,3)-sigmatropic rearrangement of 2. Attempts to detect the silylene by laser flash photolysis were unsuccessful, but the vinylsilirane could be easily detected as a long-lived transient exhibiting λ max = 285 nm and lifetime τ = 1.3 s in hexane at 25 • C. The same spectrum is observed in neat methanol solution, where the lifetime of the species is shortened to τ = 36 ms and it is quenched by sodium methoxide and methanesulfonic acid with absolute rate constants of k MeO -= 2.0 × 10 6 M −1 s −1 and k H+ = 2.6 × 10 3 M −1 s −1 , respectively. The photochemistry of 2 is compared to that of the corresponding germanium homologue (1), whose photolysis in solution has been previously shown to afford diphenylgermylene and DMB cleanly and in high yields. The corresponding vinylgermirane (11a), though not detectable as a primary photoproduct from 1 in solution, is the exclusive product of photolysis of 1 in a 3-methylpentane glass at 78 K, where it exhibits an essentially identical UV/vis spectrum to that of 9. The rate constant for its unimolecular thermal isomerization to regenerate 1 is three orders of magnitude larger than that of the corresponding process in the homologous vinylsilirane (9) in hydrocarbon solution at 25 • C.

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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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Kinetic spectroscopy of diphenylgermylene Ph2Ge following laser flash photolysis of bis(trimethylsilyl) diphenylgermane (Me3Si)2GePh2

Cited by 31 publications

References 13 publications

Substituent effects on silene reactivity — Reactive silenes from photolysis of phenylated tri- and tetrasilanes

Substituent effects on silene reactivity — Reactive silenes from photolysis of phenylated tri- and tetrasilanes

The photochemistry of a potential diphenylsilylene precursor. Time-resolved spectroscopic studies of the reactivity of a transient vinylsilirane

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

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