Mechanism of Perfluoro-Nickelacyclopentane Formation from Tetrafluoroethylene: Effects of Ancillary Ligand Bite Angle
Bibliographic record
Abstract
Metallacyclopentanes are important reaction intermediates for catalytic processes, such as selective ethylene oligomerization and diene cyclooligomerization. Reactions of fluoroalkenes with low-valent first row transition metal complexes tend to form stable fluorometallacyclopentane products. DFT studies conducted herein indicate that conversion of three-coordinate Ni(η 2 -C 2 F 4 )L 2 complexes (L 2 = 2 monodentate or one bidentate chelate) to perfluorometallacycle products Ni[κ 2 -(CF 2 ) 4 -]L 2 occurs preferentially via a four-coordinate intermediate Ni(η 2 -C 2 F 4 ) 2 L 2; an alternative three-coordinate pathway via Ni(η 2 -C 2 F 4 ) 2 L occurs only when L is extremely bulky. The transition structure for cyclization requires a dramatic increase in the L–Ni–L angle, which is perpendicular to the C–C bond-forming plane and initially affords a kinetic metallacycle intermediate resembling a trigonal bipyramidal geometry with one equatorial vacant site. The donor solvent, or intramolecular O-donor association with this intermediate, provides a low-energy pathway to the formation of the more stable square-planar metallacycle product. For bidentate chelate ligands, differential bite angles affect both coordination of a second C 2 F 4 ligand and the cyclization step. For small-bite-angle chelates, the cyclization transition state energies are higher relative to monodentate analogues. An experimental investigation of wide bite-angle bis(phosphine) ligands such as DPEphos and Bisbi showed the formation of additional nickelacyclopentane products with the coordination of a single P center to each Ni [DPEphos = bis(2-diphenylphosphino-phenyl) ether; Bisbi = 2,2′-bis(diphenylphosphino-methyl)-1,1′-biphenyl].
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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 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".