- Kinetics and mechanisms of the reactions of diaryl- and dialkylgermylenes with alcohols and ethers in solution
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The reactions of methanol, tert-butanol, and THF with a series of simple germylene derivatives-dimethyl- (GeMe2), diphenyl- (GePh 2), and dimesitylgermylene (GeMes2; Mes = 2,4,6-trimethylphenyl)-have been studied in hexane solution at 25 °C by laser flash photolysis methods. The results are consistent with rapid, reversible reaction to form weakly stabilized Lewis acid-base complexes, which exhibit UV absorption maxima in the range 290-360 nm and decay with mixed order kinetics with concomitant formation of the corresponding digermene, Ge 2R4 (R = Me, Ph, or Mes). Absolute rate constants for formation of the complexes could be measured for GePh2 with all three substrates and for GeMe2 with THF and were found to vary over the range (4-10) × 109 M-1 s-1. Equilibrium constants were measured in all cases; they vary between 1.2 and 15 M -1 for GeMes2, decreasing in the order MeOH > t-BuOH > THF, while those for GeMe2 and GePh2 are 2-4 orders of magnitude larger and decrease in the order THF > MeOH > t-BuOH. For a given substrate, the equilibrium constants are consistently larger for GePh 2 than for GeMe2, reflecting the greater ability of phenyl compared to methyl substituents to stabilize negative charge at germanium in the zwitterionic complexes. In spite of the differences in the stabilities of the complexes, the rate constant for complexation with THF is almost twice as large for GeMe2 than for GePh2. The results indicate that the O - H insertion reaction of germylenes with alcohols proceeds via initial, reversible Lewis acid - base complexation, followed by slow proton transfer from oxygen to germanium, most likely via a catalytic route.
- Leigh, William J.,Lollmahomed, Farahnaz,Harrington, Cameron R.,McDonald, Jacklyn M.
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- Stabilization of a transient diorganogermylene by an N-heterocyclic carbene
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The synthesis of a carbene-stabilized transient germylene is presented; the resulting complex liberates free germylene upon heating, forms a stable adduct with BH3, and reacts with MeLi to displace the carbene.
- Rupar, Paul A.,Jennings, Michael C.,Ragogna, Paul J.,Baines, Kim M.
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- Reactivity of sulfonyl-containing compounds with ditetrelenes
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The addition of a variety of sulfones and a sulfoxide to ditetrelenes (a disilene and a digermene) was examined. The reaction of benzenesulfonyl chloride with tetramesityldisilene or tetramesityldigermene results in the formation of the 1,2-addition products, 2-chlorotetramesityldisilyl- or digermylbenzenesulfinate. The addition of p-toluenesulfonyl chloride to the disilene gave the analogous product, 2-chlorotetramesityldisilyl p-toluenesulfinate. In contrast, benzenesulfonyl fluoride, diphenyl and dimethyl sulfone did not react with either the disilene or the digermene. The unprecedented formation of the sulfinates reveals a selective 2-electron reduction of the sulfur centres using ditetrelenes. The addition reactions of sulfonyl compounds illustrates the potential of ditetrelenes to serve as reducing agents which react rapidly, at room temperature under mild conditions. The reaction of tetramesityldisilene with diphenyl sulfoxide resulted in the formation of tetramesityloxadisilirane and with benzene sulfonic acid resulted in the formation of 1,1,2,2-tetramesityldisilyl benzenesulfonate.
- Tashkandi, Nada Y.,Bourque, Jeremy L.,Baines, Kim M.
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p. 15451 - 15457
(2017/11/21)
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- Addition of Isocyanides to Tetramesityldigermene: A Comparison of the Reactivity between Surface and Molecular Digermenes
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The reaction of benzyl isocyanide, tert-butyl isocyanide, and 2,6-dimethylphenyl isocyanide with tetramesityldigermene (Mes2Ge=GeMes2) was examined. Whereas the addition of benzyl isocyanide gave the C?NC activation product, Mes2Ge(CH2Ph)Ge(CN)Mes2, tert-butyl isocyanide, and 2,6-dimethylphenyl isocyanide did not give stable adducts, rather the rate of conversion of the digermene to the corresponding cyclotrigermane was accelerated. A comparison between the reactivity of the isocyanides with Mes2Ge=GeMes2and the Ge(100)-2×1 surface was made and some insights into the surface chemistry are offered.
- Tashkandi, Nada Y.,Cook, Emily E.,Bourque, Jeremy L.,Baines, Kim M.
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p. 14006 - 14012
(2016/09/21)
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- On the synthesis, structure, and reactivity of tetramesityldigermene
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Tetramesityldigermene (1) can be synthesized cleanly and quantitatively by photolysis of hexamesitylcyclotrigermane (2) in THF at low temperature. A solution of tetramesityldigermene (1) in THF is stable for several weeks at room temperature; the digermene does not dissociate or rearrange. The molecular structure of tetramesityldigermene (1) has been determined using X-ray crystallography. The effectiveness of the new protocol for the synthesis of tetramesityldigermene (1) and its derivatives has been demonstrated in the study of the addition of carboxylic acids to tetramesityldigermene (1).
- Hurni, Krysten L.,Rupar, Paul A.,Payne, Nicholas C.,Baines, Kim M.
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p. 5569 - 5575
(2008/10/09)
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- Organogermanium reactive intermediates. The direct detection and characterization of transient germylenes and digermenes in solution
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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.
- Leigh, William J.,Harrington, Cameron R.,Vargas-Baca, Ignacio
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p. 16105 - 16116
(2007/10/03)
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- Thermolysis of Cyclotrigermane: Simple Preparation of Digermetanes containing a Germanium-Germanium Bond
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Thermolysis of hexamesitylcyclotrigermane in the presence of paraformaldehyde, thiobenzophenone, and phenylacetylene at 80 deg C produces the corresponding adducts with tetramesityldigermene.
- Ando, Wataru,Tsumuraya, Takeshi
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p. 770 - 771
(2007/10/02)
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- Synthesis and chemistry of thiagermiranes
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Dimethylgermylene (1) reacts with thioketones 3 and 9 to give 1,3,2,4-dithiadigermolanes 4 and 10, the ultimate products of formation of thiagermiranes 6 and 11 and subsequent addition of dimethylgermanethione (7). Dimesitylgermylene (16) reacts with adamantanethione (3) to give 3-(2-adamantyl)-2,2-dimesityl-1,2-thiagermirane (18). Photolysis of thiagermirane 18 yields dimesitylgermylene (16) and adamantanethione (3) derived from germathiocarbonyl ylide 22. Oxidation of thiagermirane 18 by mCPBA gives 3-(2-adamantyl)-4,4-dimesityl-1,2,4-oxathiagermetane S-oxide (27). X-ray analyses were done for thiagermirane 18 and 1,2,4-oxathiagermetane S-oxide 27.
- Tsumuraya, Takeshi,Sato, Sadao,Ando, Wataru
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p. 161 - 167
(2008/10/08)
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- Electronic absorption spectra of diorganogermylenes in matrices: Formation of diorganogermylene complexes with heteroatom-containing substrates
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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.
- Ando, Wataru,Itoh, Hiroyuki,Tsumuraya, Takeshi
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p. 2759 - 2766
(2008/10/08)
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- Spectroscopic characterization of diarylgermylene complexes with heteroatom-containing substrates
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Characteristic UV absorption bands of diarylgermylene complexes were observed in the reaction of diarylgermylenes with heteroatom-containing substrates in 3-MP/IP matrix at 77 K.
- Ando, Wataru,Itoh, Hiroyuki,Tsumuraya, Takeshi,Yoshida, Hitoaki
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p. 1880 - 1882
(2008/10/08)
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- Matrix Isolation and Ultraviolet Spectra of Germylenes
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Some organogernylenes were isolated in a hydrocarbon matrix at low temperature by the photolysis of 7-germanoboradienes or bis(trimethylsilyl)germanes.The germylenes show electronic absorption bands at 420-560 nm.
- Ando, Wataru,Tsumuraya, Takeshi,Sekiguchi, Akira
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p. 317 - 318
(2007/10/02)
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