Synthesis and Chemistry of Zwitterionic Tantala-3-boratacyclopentenes: Olefin-like Reactivity of a Borataalkene Ligand
Bibliographic record
Abstract
The compounds, where Cp' = C(5)H(5), a series, and C(5)H(4)Me, b series, are generated via treatment of with HB(C(6)F(5))(2). When allowed to undergo irreversible methane loss in the presence of an excess of the sterically modest alkynes 2-butyne or phenylacetylene, the putative intermediates 1a and 1b are trapped as the tantala-3-boratacyclopentene compounds 2 and 3, respectively. In these complexes, the alkyne and borataalkene ligands have reductively coupled at the d(2) tantalum center. For the unsymmetrical alkyne, a kinetic product resulting from coupling in the opposite regiochemical sense is observed; the thermodynamic products 3-t incorporate the phenyl group in the alpha position of the tantalaboratacyclic ring. Two of these compounds (2b and 3b-t) were characterized crystallographically. For bulkier alkynes (diphenylacetylene, 1-phenyl-1-propyne, and 3-hexyne), intermediates with similar spectroscopic properties to the tantala-3-boratacyclopentenes were observed, but the ultimate products were the vinylalkylidene compounds 5-(R,R'). Compound 5-(Ph,Me) was characterized crystallographically, and it was found that the vinylalkylidene binds to the metal in an eta(1)-bonding mode, with the tantalum center receiving further ligation through a hydridoborate moiety. Mechanistic studies suggest that these products arise via retrocyclization of the tantala-3-boratacyclopentenes formed kinetically. These studies represent the first studies concerning the reactivity of a borataalkene ligand at a transition metal center and show that it can behave in an "olefin-like" manner, despite having a more flexible array of bonding modes available to it than an olefin.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 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".