Formation and reactivity of the zirconium ethylene complexes [η<sup>5</sup>-C<sub>5</sub>H<sub>3</sub>-1,3-(SiMe<sub>2</sub>CH<sub>2</sub>PR<sub>2</sub>)<sub>2</sub>]Zr(η<sup>2</sup>-CH<sub>2</sub>=CH<sub>2</sub>)(X) (R = Me, Pr<i><sup> i</sup></i>; X = Br, C<sub>5</sub>H<sub>5</sub>)
Bibliographic record
Abstract
The formation and reactivity of the zirconium ethylene complexes R[P2Cp]Zr(η2-CH2=CH2)(X) (2a: R = Pri, X = Br; 2b: R = Me, X = Br; 4a: R = Pri, X = C5H5; R[P2Cp] = (η5-C5H3-1,3-(SiMe2CH2PR2)2)) are described. Ethylene complexes 2a and 2b are prepared from a reaction of R[P2Cp]ZrCl3 (1a: R = Pri; 1b: R = Me) with 2 equiv of EtMgBr, presumably via β-H elimination from the diethyl intermediate R[P2Cp]ZrCl(CH2CH3)2. The structure of 2b was determined by X-ray crystallography. Addition of carbon monoxide to 16-electron 2 displaces the ethylene ligand to generate the carbonyl complex R[P2Cp]Zr(CO)2Br (5a: R = Pri; 5b: R = Me), which is stable only under an atmosphere of CO. The corresponding CO reaction with 18-electron 4a to give the metallocene monocarbonyl analogue Pr[P2Cp]Zr(η5-C5H5)(CO) (6a) is considerably slower. 2a exhibits fluxional exchange of one carbonyl ligand with bulk 13CO in solution; the kinetic parameters for this exchange process are ΔH = 9.2(5) kcal mol1 and ΔS = 17(2) cal mol1 K1. The addition of diphenylacetylene to 2a yields the alkyne complex Pr[P2Cp]Zr(η2-PhCCPh)Br (7a), which exists in solution as two isomers in equilibrium. A solid-state X-ray structure determination for the minor isomer syn-7a was performed.Key words: zirconium, cyclopentadienyl phosphine, alkyne, metallocyclopropane.
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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 | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".