Dynamic Behavior of Hydrogen in Transition Metal Bis(silyl) Hydride Complexes
Bibliographic record
Abstract
A series of rhodium complexes CpRh(SiMe 2 X) 2 (SiMe 3 )(H) (X = Me, Cl, Br, I), Cp1 – Cp4, CpRh(SiMe 2 X) 2 (PMe 3 )(H) + (X = Me, Cl, Br, I), Cp5 – Cp8, CpRh(SiMe 3 ) 2 (SiF 3 )(H), Cp9, CpRh(SiMe 3 ) 2 (SiH 3 )(H), Cp10, TpRh(SiH 3 ) 2 (SiMe 3 )(H), Tp1, TpRh(SiH 3 ) 2 (PMe 3 )(H) +, Tp2, and TpRh(SiF 3 ) 2 (PMe 3 )(H) +, Tp3, were studied computationally to understand the hydrogen behavior in the Si···H···Si moiety. The hydride ligand interacts with at least one of the silyls, and in many cases with both, but is located asymmetrically with regard to them, giving rise to a double-well potential energy surface (PES) for hydrogen motion. The hydrogen transfer barriers Δ E vary from 0.03 to 3 kcal·mol –1 . For selected complexes Tp1, Tp2, Tp3, and Cp9 the three-dimensional PESs were constructed and the vibrational Schrödinger equation was solved. The PES is highly anharmonic in all four cases. The hydrogen is delocalized between two silicons in complexes Tp1, Tp3, and Cp9, but localized around the energy minima in complex Tp2 . Complex Tp3 is an intermediate case with a substantial tunneling. The delocalized behavior is pertinent to systems with Δ E < 0.25 kcal·mol –1 . For complexes Tp1, Tp2, Tp3, and Cp9 the J (Si–H) spin–spin coupling constants were calculated taking into account the vibrational motion of hydride. For Tp1, Tp3, and Cp9 both J (Si 1 –H) and J (Si 2 –H) are negative due to simultaneous Si 1 ···H···Si 2 interactions, while for Tp2 J (Si 2 –H) is positive, indicating a single Si···H interaction only. Negative J (Si–H) values were obtained even for Si···H distances as large as 2.3 Å (complex Tp3 ). A possible effect of vibrations on the J (Si–H) values is also discussed.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".