Polymerization Catalysts with d<i><sup>n</sup></i> Electrons (<i>n</i> = 1−4): A Theoretical Study
Bibliographic record
Abstract
We present an investigation on the potential of first-row transition metals with a d-electron count from 1 to 4 as olefin polymerization catalysts by means of first-principles density functional theory (DFT) type calculations. We considered generic model systems [MLL‘R] + with M = Ti, V, Cr, and Mn (R = Me, Et) in high-spin electron configuration bearing two nitrogen ligands L,L‘ (NH 2 - and NH 3 ) in order to elucidate the effect of partially filled d-levels on the elementary steps of ethylene polymerization. The olefin uptake energy is found to diminish almost linearly with an increasing number of d-electrons due to a successive destabilization of the metal acceptor orbital. Ethylene insertion barriers were calculated to be between 6 and 16 kcal/mol (R = Et) and are less affected by the d-electron count than by the type of the transition metal and its oxidation state. The dominant termination process for most systems is a β-hydrogen transfer (BHT) to the monomer. Its barrier follows the trends of the olefin insertion, but is higher in absolute values for the majority of systems. In the case of the Cr(IV) d 2 system, with the overall best performance, possible real size catalysts were investigated. It is shown that by taking the specific electronic situation in d n systems into account, olefin insertion barriers below 10 kcal/mol together with high termination barriers can be achieved.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.184 | 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 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".