5764-69-2Relevant academic research and scientific papers
Competing germene and germylene extrusion from photolysis of 1,1-diarylgermacyclobutanes. Substituent effects on germene reactivity
Leigh, William J.,Potter, Gregory D.,Huck, Lawrence A.,Bhattacharya, Adroha
, p. 5948 - 5959 (2009/04/13)
Direct irradiation of 1,1-diphenyl-, 1,1-bis[4-(trifluoromethyl)phenyl]-, and 1,1-bis[3,5-bis(trifluoromethyl)phenyl]germacyclobutanes (2, 4, and 5, respectively) in methanolic C6D12 solution affords products consistent with the competing formation of the corresponding 1,1-diarylgermenes and diarylgermylenes, along with ethylene and cyclopropane. The relative yields of the two Ge-containing primary products (germene:germylene) vary with the extent of CF3 substitution on the aryl rings, decreasing in the order 2 > 4 > 5. As was reported previously for 2, laser flash photolysis of 4 and 5 in hexane, acetonitrile, or tetrahydrofuran solution allows the detection of the corresponding transient 1,1 -diarylgermenes (6 and 7, respectively), which have been identified on the basis of their UV/vis spectra (λmax ～325 nm) and quenching studies with MeOH, tert-butyl alcohol (t-BuOH), acetic acid (AcOH), n-butylamine (M-BuNH2), and acetone. In carefully dried hexane solution, weak transient absorptions assignable to the corresponding germylenes and their respective (digermene) dimers are also observed; in the case of 5, these assignments have been confirmed by the results of steady-state and laser photolysis experiments with 1,1-bis[3,5-bis(trifluoromethyl)phenyl]-2,3- dimethyl-1-germacyclopent-3-ene (14c), which affords the germylene exclusively, in substantially higher quantum yield. The reactivities of the germenes toward each of the various substrates studied vary modestly with aryl substituent, increasing in the order acetone 2 a much more dominant role in the reactions of the Ge=C bond with nucleophilic reagents than is the case with the homologous silene derivatives, whose reaction kinetics are controlled primarily by substrate nucleophilicity.
Time-resolved spectroscopic studies of the photochemistry of some diphenylgermylene (Ph2Ge:) precursors
Harrington, Cameron R.,Leigh, William J.,Chan, Bryan K.,Gaspar, Peter P.,Zhou, Dong
, p. 1324 - 1338 (2007/10/03)
The photochemistry of diphenylbis(trimethylsilyl)germane (2a) and 1,4-dihydro-5-methyl-1,2,3,4,9,9-hexaphenyl-1,4-germanonaphthalene (11) has been studied in solution by steady-state and laser flash photolysis methods with a view to detecting the transient germylene derivative diphenylgermylene (Ph 2Ge), which has previously been shown to be the major product of photolysis of 2a and a closely related derivative of 11. Steady-state trapping experiments confirm the formation of Ph2Ge as the major germanium containing primary product in both cases; with 2a, the results indicate that other transient species are also formed in minor yields, including phenyl(trimethylsilyl)germylene (Ph(TMS)Ge, ca. 6%) and diphenyl(trimethylsilyl) germyl radicals (Ph2(TMS)Ge, ≥15%). Laser flash photolysis of 2a in deoxygenated hexane solution yields a complex mixture of overlapping transient absorptions, which is shown to be comprised of Ph2Ge, tetraphenyldigermene (15) and its oligomerization products, and another species with spectral characteristics similar to the Ph2(TMS)Ge radical. The latter has been independently generated by hydrogen abstraction from diphenyl(trimethylsilyl)germane by tert-butoxyl radicals. Compound 11 extrudes Ph2Ge more cleanly and efficiently upon photolysis in solution, yet laser flash photolysis affords excited triplet and triplet-derived species as the only detectable transient products; interpretation of the results for this compound is made difficult by its slow thermal decomposition to 5-methyl-1,2,3,4-tetraphenylnaphthalene. It is concluded that in spite of the fact that both 2a and 11 afford Ph2Ge in high yield upon photolysis, they are poor precursors for study of the species in solution by time-resolved UV-vis methods, owing to the formation of other, more strongly absorbing transient products than Ph2Ge, whose lowest energy absorption is characteristically weak.
Organogermanium reactive intermediates. The direct detection and characterization of transient germylenes and digermenes in solution
Leigh, William J.,Harrington, Cameron R.,Vargas-Baca, Ignacio
, p. 16105 - 16116 (2007/10/03)
Diphenylgermylene (Ph2Ge) and its Ge=Ge doubly bonded dimer, tetraphenyldigermene (6a), have been characterized directly in solution for the first time by laser flash photolysis methods. The germylene is formed via (formal) cheletropic photocycloreversion of 3,4-dimethyl-1,1- diphenylgermacyclopent-3-ene (4a), which is shown to proceed in high chemical (>95%) and quantum yield (Φ = 0.62) by steady-state trapping experiments with methanol, acetic acid, isoprene, and triethylsilane. Flash photolysis of 4a in dry deoxygenated hexane at 23°C leads to the prompt formation of a transient assigned to Ph2Ge (∈max = 500 nm; ∈max = 1650 M-1 cm-1), which decays with second-order kinetics (τ ≈ 3 μs), with the concomitant growth of a second transient species that is assigned to digermene 6a (τ ≈ 40 μs; λmax = 440 nm). Analogous results are obtained from 1,1-dimesityl- and 1,1-dimethyl-3,4-dimethylgermacyclopent-3-ene (4b and 4c, respectively), which afford Mes2Ge (τ = 20 μs; λmax = 560 nm) and Me2Ge (τ ≈ 2 μs; λs; λmax = 480 nm), respectively, as well as the corresponding digermenes, tetramesityl- (6b; λmax = 410 nm) and tetramethyldigermene (6c; λmax = 370 nm). The results for the mesityl compound are compared to the analogous ones from laser flash photolysis of the known Mes2Ge/6b precursor, hexamesitylcyclotrigermane. The spectra of the three germylenes and two of the digermenes are in excellent agreement with calculated spectra, derived from time-dependent DFT calculations. Absolute rate constants for dimerization of Ph2Ge and Mes2Ge and for their reaction with n-butylamine and acetic acid in hexane at 23°C are also reported.
Photochemistry of group 14 1,1,1-trimethyl-2,2,2-triphenyldimetallanes (Ph3MM′Me3; M, M′ = Si, Ge). Direct detection and characterization of silene and germene reactive intermediates
Leigh, William J.,Toltl, Nicholas P.,Apodaca, Paula,Castruita, Madeli,Pannell, Keith H.
, p. 3232 - 3241 (2008/10/08)
The photochemistry of trimethylsilyltriphenylgermane (Ph3GeSiMe3), triphenylsilyltrimethylgermane (Ph3SiGeMe3), and 1,1,1-trimethyl-2,2,2-triphenyldigermane (Ph3GeGeMe3) has been studied in hydrocarbon solution by steady state and laser flash photolysis methods and is compared to previously reported data for the homologous disilane Ph3SiSiMe3. A variety of products are formed upon photolysis of the three compounds in the presence of 2,3-dimethyl-1,3-butadiene or chloroform, but in each case the major ones are derived from M-M′ bond homolysis and dimethyl- or diphenylgermylene extrusion. The trapping products of the 1,3,5-(1-metalla)hexatriene derivatives formed by [1,3]-MMe3 migration into the ortho-position of one of the phenyl rings are formed as well, in yields of 9-30%. While these experiments indicate that germylenes are formed in at least twice the yield of the 1,3,5-(1-metalla)hexatrienes, only the latter and triphenylsilyl or triphenylgermyl radicals can be detected by laser flash photolysis techniques. The metallaenes have been identified on the basis of their time-resolved UV absorption spectra and absolute rate constants for reaction with 2,3-dimethylbutadiene, methanol, acetone, acetic acid, oxygen, and carbon tetrachloride and can be distinguished from germylenes by their lack of reactivity toward triethylsilane and chloroform. Radical formation is shown to result from reaction of the triplet states of these compounds, and a triplet lifetime is estimated for Ph3GeSiMe3 and compared to that of the disilane homologue. The results of time-resolved experiments on other, related compounds are discussed in light of these results.
New photochemical routes to germylenes and germenes and kinetic evidence concerning the germylene-diene addition mechanism
Bobbitt, Kevin L.,Maloney, Vincent M.,Gaspar, Peter P.
, p. 2772 - 2777 (2008/10/08)
Upon 254-nm irradiation of phenylbis(trimethylsilyl)germanes, there is competition between two germylene-forming reactions, the unexpected elimination of phenyltrimethylsilane and the elimination of hexamethyldisilane. Irradiation of a phenylmonosilylgermane PhGeMe2SiMe3 leads to predominant elimination of PhSiMe3, forming dimethylgermylene Me2Ge:, accompanied by migration of Me3Si to the ortho position of the phenyl ring, forming a germene. Laser flash photolysis of PhGeMe2SiMe3 is a convenient source of Me3Ge:, and rate constants are reported for Me2Ge: addition to a series of dienes and other substrates. The kinetic data are in accord with 1,2-addition as the dominant pathway for addition of Me2Ge: to 1,3-dienes.
Photochemistry of aryl-substituted trigermanes. Generation and mechanism of formation of germylenes
Mochida, Kunio,Yoneda, Isao,Wakasa, Masanobu
, p. 53 - 62 (2007/10/02)
Photochemical reactions of aryl-substituted trigermanes have studied by trapping experiments, matrix isolation, and laser flash-photolysis techniques.Photolysis of the phenylated trigermanes involved both the simple extrusion of germylenes and the formati
Electronic absorption spectra of diorganogermylenes in matrices: Formation of diorganogermylene complexes with heteroatom-containing substrates
Ando, Wataru,Itoh, Hiroyuki,Tsumuraya, Takeshi
, p. 2759 - 2766 (2008/10/08)
Diorganogermylenes were generated in hydrocarbon matrices at 77 K by the photolysis of 7-germanorbornadienes 1a-e or bis(trimethylsilyl)germanes 2a-g. The germylenes show electronic absorption bands at 420-558 nm. The germylenes react with heteroatom-containing substrates (R2O, R2S, R3P, R3N, RCl, and ROH) to form adducts, which show characteristic absorption bands at shorter wavelengths than those of germylenes.
Photochemistry of aryl-substituted trigermanes
Wakasa, Masanobu,Yoneda, Isao,Mochida, Kunio
, p. C1 - C5 (2007/10/02)
The photolysis of phenyl-substituted trigermanes affords digermanes and germenylenes.Trapping experiments, matrix isolation, and laser-photolysis studies indicate that the photoreaction of these compounds involves both the extrusion of germylenes and the
Preliminary communication. Kinetic spectroscopy of diphenylgermylene Ph2Ge following laser flash photolysis of bis(trimethylsilyl)diphenylgermane (Me3Si)2GePh2
Konieczny, Stanislaw,Jacobs, S. Joshua,Wilking, Janet K. Braddock,Gaspar, Peter Paul
, p. C17 - C22 (2007/10/02)
A transient, λmax 445 nm, was observed in the 266 nm laser flash photolysis of cyclohexane solutions of (Me3Si)2GePh2, and rate constants were recorded for its disappearance in the presence of various trapping agents.The reactivity profile is in accord with the identification of the carrier as diphenylgermylene Ph2Ge, that dimerizes to tetraphenyldigermene Ph2Ge=GePh2, λ7max3 320 nm.
Untersuchungen von Diiodogermylen und Triphenylphosphindiiodogermylen und die Kristallstruktur von Triphenylphosphindiiodogermylen
Inoguchi, Yoshio,Okui, Shuko,Mochida, Kunio,Itai, Akiko
, p. 974 - 977 (2007/10/02)
Reaktivitaeten und chemische Eigenschaften von Diiodogermylen und Triphenylphosphindiiodogermylen wurden durch ihre Reaktionen mit Organolithium-Verbindungen oder Butadienen untersucht.Die Kristallstruktur von Triphenylphosphindiiodogermylen wurde roentgenographisch aufgeklaert.
