The insertion of germylene into the HH bond; rate constant limits and thermochemistry. Ab initio and DFT calculations on the reactions of GeH<sub>2</sub> and SiH<sub>2</sub> with H<sub>2</sub>
Bibliographic record
Abstract
The technique of laser flash photolysis in the gas-phase has been used to set limits on the rate constants for the bimolecular reaction of germylene (GeH 2 ) with deuterium (D 2 ) at both ambient and elevated temperatures (585 K). These limits show that the activation energy for the insertion of GeH 2 into the HH bond is at least 19 (±6) kJ mol 1 . Thermochemical arguments place the activation energy approximately in the range 6384 kJ mol 1 . DFT B3LYP/6-311++G(3df,2pd) and ab initio QCISD(T)/6-311G++(3df,2pd)//QCISD/6-311G(d,p) calculations have been carried out on the potential energy surfaces of reactions ZH 2 + H 2 [Formula: see text] ZH 4 (Z= Ge, Si). Both methods predict the same mechanisms for germylene and silylene insertion which include formation of loose prereaction complexes and transition states of similar structure. The prereaction complex is only about half as strong in the case of germylene (ΔH (298 K) = 9 (11) kJ mol 1 ) as in the case of silylene (ΔH (298 K) = 16 (21) kJ mol 1 ) (QCISD values cited with B3LYP values in parentheses). The differences in activation energies are even more significant. Germylene insertion has a very high barrier of 58 (56) kJ mol 1 compared to that of silylene 13 (6) kJ mol 1 . Calculated activation parameters for both reactions are in reasonable consistency with experimental results. Reasons for the enhanced HH insertion barrier for germylene compared with silylene are discussed.Key words: laser flash photolysis, germylene, silylene, deuterium, activation energy, thermochemistry, ab initio calculation, DFT B3LYP calculation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".