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• 67-56-1 methanol 
• 5764-69-2 1,1-diphenyl-3,4-dimethyl-1-germacyclopent-3-ene 

Relevant academic research and scientific papers

Kinetics and mechanisms of the reactions of diaryl- and dialkylgermylenes with alcohols and ethers in solution

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.

Organogermanium reactive intermediates. The direct detection and characterization of transient germylenes and digermenes in solution

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.