Fast Kinetic Studies of the Reactivities of Transient Germylenes in Methanol and Tetrahydrofuran Solution
Bibliographic record
Abstract
Laser flash photolysis techniques have been employed to study the reactivities of dimethylgermylene (GeMe 2 ), diphenylgermylene (GePh 2 ), and a series of ring-substituted diarylgermylenes (GeAr 2 ) in methanol (MeOH) and tetrahydrofuran (THF) solution, where the germylenes exist as the corresponding Lewis acid−base complexes with the O-donor solvents. Dimerization to the corresponding digermene is a significant mode of decay in THF solution, particularly for the GeMe 2 −THF complex, though for the diaryl systems it is slowed dramatically compared to the situation in hexane solution. On the other hand, dimerization is undetectable in MeOH, where the GeAr 2 −MeOH complexes decay with pseudo-first-order kinetics at low laser intensities and lifetimes in the 20−50 μs range; the GeMe 2 −MeOH complex exhibits a lifetime of ca. 4 μs under similar conditions. Solvent kinetic isotope effects are consistent with solvent-catalyzed proton transfer to yield the corresponding alkoxyhydridogermane as the process responsible for the decay of the germylene−MeOH complexes. Their decay is accelerated by strong acids and bases such as methanesulfonic acid and sodium methoxide, respectively, which quench the GePh 2 −MeOH complex with rate constants of ca. 3 × 10 9 M −1 s −1 in each case. Kinetic isotope and substituent effects are consistent with rate-determining protonation at germanium in the reactions with acid, while the results for methoxide quenching are consistent with the formation of the corresponding Ar 2 (MeO)Ge − anion as a discrete intermediate, which has been detected in MeOH solution in one instance. Reaction of sodium methoxide with the germylene−THF complexes also proceeds rapidly and allows the detection of the corresponding Ar 2 (MeO)Ge − anions and determination of rate coefficients for their protonation by MeOH, for all four of the diaryl systems that were studied. The reactivity of the GeMe 2 −THF complex toward sodium methoxide, methanesulfonic and acetic acid, CCl 4, oxygen, isoprene, and 4,4-dimethyl-1-pentene has also been examined.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".