Coordination and Reactivity Study of Group 4 and 10 Transition Metal Complexes of<i>N</i>-Imidazol-2-ylidene-<i>N</i>′-<i>p</i>-tolylureate and Thioureate Ligands
Bibliographic record
Abstract
The synthesis and isolation of N -imidazol-2-ylidene- N ′- p -tolylureate and thioureate proligands is described. Titanium(IV), nickel(II), and palladium(II) complexes containing one or two equivalents of the ligand were prepared by transmetalation of the ureate or thioureate salts. The X-ray structure of titanium complexes corroborated our prediction based on spectroscopic data and showed the ureate binds in a bidentate fashion through the oxygen and nitrogen atoms of the isocyanate building block, leaving the imidazol-2-imine fragment uncoordinated. Carbon–nitrogen bond lengths indicate substantial electron delocalization from the imidazole ring to the ureate group. In contrast, the ligand adopts a different coordination mode and binds to nickel and palladium through the N imidazol-2-ylidene and N p- tolyl atoms. Surprisingly, despite the softer nature of sulfur, coordination of the thioureate was exclusively through the sulfur and nitrogen atoms of the isothiocyanate building block with all three metals studied. All complexes were tested for ethylene polymerization at ambient conditions using methylaluminoxane as cocatalyst. Titanium(IV) complexes were found to be the most active, with activities up to 60 kg PE mol –1 catalyst h –1 .
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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 | 0.000 | 0.000 |
| Open science | 0.001 | 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".