72876-20-1Relevant academic research and scientific papers
Preparation, Structure, and 73Ge NMR Spectroscopy of Arylgermanes ArGeH3, Ar2GeH2, and Ar3GeH
Riedmiller, Frank,Wegner, Gerald L.,Jockisch, Alexander,Schmidbaur, Hubert
, p. 4317 - 4324 (2008/10/08)
Arylgermanes of the types ArGeH3, At2GeH2, and Ar3GeH are important precursors for the preparation of oligo- and polygermanes. These precursors are readily prepared in good yields via an in situ Grignard reaction employing tetra(ethoxy)germane, an aryl halide, and magnesium metal in tetrahydrofuran as the reaction medium. The aryl-tri(ethoxy)germanes obtained were reduced to the germane hydrides with LiAIH4. This method is also applicable for aryl groups with sensitive substituents, as demonstrated for (4-methoxyphenyl)germane (p-anisylgermane, MeOC6H4GeHa). With modified stoichiometry, bis(p-anisyl)gennane is also available. The insertion of GeCI2 into the C-Br bond of arylbromides using catalytic amounts of anhydrous Aids proved to be an efficient alternative if the reaction was carried out in the absence of a solvent. After LiAlH4 reduction of the aryltrihalogermanes, phenyl-,p-tolyl-, and mesitylgermane were obtained in good yields. The arylgermanes have been identified by their analytical and spectroscopic data, including 73Ge (s = 9/2) NMR spectroscopy. Very surprisingly, sharp multiplet signals were observed with well-resolved 1J(Ge,H) couplings. The molecular structure of p-MeOC6H4GeH3 was determined from low-temperature X-ray diffraction data collected from a single-crystal grown "in situ" from the melt (mp: 15 °C). The significant distortions observed in the anisyl part of the structure and the conformation of the molecule are in excellent agreement with results of ab initio quantum chemical calculations (MP2/6-31G) of this compound.
Hydrogen Donor Abilities of Germanium Hydrides
Chatgilialoglu, Chryssostomos,Ballestri, Marco,Escudié, Jean,Pailhous, Isabelle
, p. 2395 - 2397 (2008/10/08)
Rate constants for the reaction of primary alkyl radicals with a variety of germanium hydrides have been measured by using the one-carbon ring expansion of cyclopentanones as a timing device. The radical-trapping abilities of these germanes and other common group 14 hydrides are compared.
The prototype Ge-H insertion reaction of germylene with germane. Absolute rate constants, temperature dependence, RRKM modeling and the potential energy surface
Beccera, Rosa,Boganov, Sergei E.,Egorov, Mikhail P.,Faustov, Valery I.,Nefedov, Oleg M.,Walsh, Robin
, p. 12657 - 12665 (2008/10/08)
Time-resolved studies of germylene, GeH2, generated by laser flash photolysis of 3,4-dimethyl-germacyclopentene-3, have been carried out to obtain rate constants for its bimolecular reaction with monogermane, GeH4. The reaction was studied in the gas phase over the pressure range 1-100 Torr, with SF6 as bath gas, at five temperatures in the range 292-520 K. The reaction of GeH2 with GeH4 to form digermane, Ge2H6, is pressure dependent, consistent with a third-body assisted association reaction. The high-pressure rate constants, obtained by extrapolation, gave the following Arrhenius equation: log(k∞/cm3 molecule-1 s-1) = (-11.17 ± 0.10) + (5.2 ± 0.7 kJ mol-1)/RT ln 10. These Arrhenius parameters are consistent with a moderately fast reaction occurring at approximately one-fifth of the collision rate. RRKM modeling, based on a variational transition state, used in combination with a weak collisional deactivation model, gave good fits to the pressure dependent curves, for a suitable choice of the critical energy, E(o), for reverse decomposition of Ge2H6. The step size (energy removed in a down collision) was chosen by analogy with the corresponding system for Si2H6 (collisional efficiency (β(c)) of ca. 0.7 for SF6). The value obtained for E(o) was 155 kJ mol-1. Corrected for thermal energy and combined with the insertion activation energy this gives ΔH°= 166 kJ mol- 1 for the decomposition of Ge2H6. There is no previous experimental determination of this quantity. From it we derive ΔH(f)°(GeH2) = 237 ± 12 kJ mol-1, in reasonable agreement with earlier estimates. From bond dissociation energy values the Divalent State Stabilization Energy (DSSE) of germylene (119 kJ mol-1) is larger than that of silylene (94 k J mol-1). Ab initio calculations at the correlated level reveal the presence of two weak complexes (local energy minima) on the potential energy surface corresponding to either direct or inverted geometry of the inserting germylene fragment. Surprisingly, the latter is the lower in energy, lying 25 kJ mol-1 below the unassociated reactants. These complexes rearrange to digermane with very low barriers. The implications of these findings and the nature of the insertion process are discussed.
Improved synthesis of 1,2-dichlorotetramesityldigermane and other mesitylgermanes
Cooke, Jeffrey A.,Dixon, Craig E.,Netherton, Matthew R.,Kollegger, Gerlinde M.,Baines, Kim M.
, p. 1205 - 1217 (2008/10/09)
An improved procedure for the synthesis of 1,2-dichlorotetramesityldigermane is reported.
Nouveaux aryldihydrogermyllithium
Castel, A.,Riviere, P.,Satge, J.,Desor, D.
, p. 49 - 61 (2007/10/02)
The new aryldihydrogermyllithium complexes RH2GeLi (R = Ph, Mes) are prepared, in good yields, by metallation of the parent trihydrogermane with t-butyllithium in THF.They are characterized by alkylation reactions with MeI.Some germylation reactions are reported: they lead to the formation of new functional aryldihydrogermanes and aryldigermanes by a nucleophilic substitution.These aryldihydrogermyllithium complexes react also with acyl chlorides RCOCl (R = Ph, Mes) to give new diacyl- and triacyl-germanes.These easily add to the carbonyl group of aromatic aldehydes, thereby giving the corresponding α-germyl alcohols.
