Silyl Hydrides of Tantalum Supported by Cyclopentadienyl-imido Ligand Sets: Syntheses, X-ray, NMR, and DFT Studies
Bibliographic record
Abstract
Reactions of the imido complex Cp(ArN)Ta(PMe 3 ) 2 ( 1, Ar = 2,6-diisopropylphenyl) with silanes afford the silyl hydrides Cp(ArN)Ta(PMe 3 )(H)(SiR n Cl 3− n ) ( 2b − e ) and Cp(ArN)Ta(PMe 3 )(H)(SiPhMeH) ( 2a ) as the first kinetic products. However, the hydride compounds Cp(ArN)Ta(PMe 3 )(H)(SiR n Cl 3− n ) are metastable and, first, rearrange in the presence of phosphine to the chlorides Cp(ArN)Ta(PMe 3 )(Cl)(SiHR n Cl 2− n ) ( 5 ) and then decompose to Cp(ArN)Ta(PMe 3 )(Cl)(H) ( 4 ) and eventually to Cp(ArN)Ta(PMe 3 )Cl 2 ( 3 ). Complexes with a smaller Ar′ substituent at nitrogen (Ar′ = 2,6-dimethylphenyl) react faster, as do more Lewis acidic silanes. The occurrence of interligand hypervalent interactions in the tantalum complexes Cp(ArN)Ta(PMe 3 )(H)(SiR n Cl 3− n ) has been revealed by X-ray structure analysis, DFT calculations, and the experimental determination of the sign of the coupling constant J (Si−H). The J (Si−H) was found to be negative for Cp(ArN)Ta(PMe 3 )(H)(SiMe n Cl 3− n ) ( J (Si−H) = −40 Hz for n = 1; J (Si−H) = −50 Hz for n = 0), indicative of the presence of Si−H bonding, but positive for Cp(ArN)Ta(PMe 3 )(H)(SiMeHPh) ( J (Si−H) = +14 Hz), suggesting the absence of direct Si−H interactions. A DFT study of the mechanism of silane coupling with the model imido complex Cp(MeN)Ta(PMe 3 ) 2 established the feasibility of the direct addition of silanes HSiMe n Cl 3− n ( n = 1−3) to the imido group to give the adduct Cp(MeN{→SiR 3 -H})Ta(PMe 3 ) 2, as previously found in the related niobium chemistry.
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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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".