Ethylene and 1-hexene polymerization using zirconium iminophosphonamide complexes
Bibliographic record
Abstract
Ethylene polymerization was studied using a variety of iminophosphonamide (PN 2 ) complexes of zirconium. Bis(PN 2 ) dichloride complexes [Ph 2 P(NR′) 2 ] 2 ZrX 2 (X = Cl; 1a: R′ = p-tolyl; 1b: R′ = Bn; 1c: R′ = C 6 F 5 ) or dimethyl complexes (X = Me; 2a: R′ = p-tolyl; 2b: R′ = Bn) and cyclopentadienyl(PN 2 )zirconium dichloride complexes [η 5 -C 5 R′′ 5 ][R 2 P(NR′) 2 ]ZrCl 2 (3a: R′ = p-tolyl, R = Ph, R′′ = H; 3b: R′ = SiMe 3 , R = Et, R′′ = H; 3c: R′ = C 6 F 5 , R = Ph, R′′ = H; 3e: R′ = 3,5-(CF 3 ) 2 Ph, R = Ph, R′′ = H; 3f: R′ = 3,5-(CF 3 ) 2 Ph, R = Ph, R′′ = Me) or dimethyl analogs [η 5 -C 5 H 5 ][R 2 P(NR′) 2 ]ZrMe 2 (4a: R′ = p-tolyl, R = Ph; 4b: R′ = SiMe 3 , R = Et) were evaluated under a range of conditions using methylaluminoxane (PMAO) activator. Complexes 1 and 2 behave as precursors to single-site polymerization catalysts under the conditions studied, while complexes 3 or dialkyls 4 show more complex behavior and formation of poly(ethylene) with a bimodal molecular weight distribution. In contrast, activation of dialkyl complexes 4 with [Ph 3 C][B(C 6 F 5 ) 4 ] and polymerization in the presence of small amounts of PMAO or TIBAL as scavenger, led to single-site behavior. PMAO reacts with the neutral dialkyls via ligand abstraction to produce a number of P-containing species that may explain the multi-site behavior observed when using this activator. Dialkyls 4 react cleanly with [Ph 3 C][B(C 6 F 5 ) 4 ] in haloarene or even dichloromethane solution to furnish the corresponding cationic alkyls 5, which were characterized by multinuclear NMR spectroscopy. Fluxional dinuclear species are formed in the presence of excess dialkyl and these are susceptible to CH activation to form µ-Me,µ-CH 2 complexes one of which could be isolated in pure form. The cationic alkyls initiate the polymerization of 1-hexene at room temperature in chlorobenzene solution, but extensive chain transfer occurs and the systems are not living.Key words: single site, early metal olefin polymerization catalysis.
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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 | 0.000 | 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) | 0.008 | 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".