Possible Side Reactions Due to Water in Emulsion Polymerization by Late Transition Metal Complexes II: Deactivation of the Catalyst by a Wacker-Type Reaction
Bibliographic record
Abstract
The transition metal catalyzed ethylene polymerization in water suspensions has been increasingly successful in the last couple of years. Water, however, adversely affects the polymerization process by deactivating the catalyst in a Wacker-type reaction. The cationic Pd(II)-diimine Brookhart catalyst 1 is studied here by a combination of quantum mechanics and molecular mechanics to determine the nature of the decomposition reaction. The study considers the decomposition process to take place in two stages. In the first stage, a coordinated olefin is attacked by a hydroxide group to ultimately produce a β-hydroxy-ethyl complex 2 . The second step represents a decomposition to acetaldehyde and Pd(0), the latter in the form of palladium black. For the attack of OH on the coordinated ethylene in 1, both an internal path involving transfer from a palladium-coordinated OH group produced from hydrolysis of a Pd−CH 3 bond and an external path based on attack of H 2 O on coordinated ethylene were considered. Both paths are found to be feasible. For the second stage the most promising decomposition mode involves isomerization of 2 to the α-hydroxy-ethyl complex 5 followed by abstraction of a proton from the C−OH link to produce the Pd(0)-η 2 -acetaldehyde complex 12 . Finally, 12 releases acetaldehyde under the deposition of Pd(0) as palladium black.
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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) | 0.001 | 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".