Pyridine− and Imidazole−Phosphinimine Bidentate Ligand Complexes: Considerations for Ethylene Oligomerization Catalysts
Bibliographic record
Abstract
The series of 2-substituted diphenylphosphine pyridines 1 − 5 were synthesized and subsequently oxidized with silyl or aryl azides to give the series of pyridine−phosphinimine ligands 2-(Me 3 SiNPPh 2 )C 5 H 4 N ( 9 ), 2-(2,6-Me 2 C 6 H 3 NPPh 2 )C 5 H 4 N ( 10 ), 2-(2,6- i- Pr 2 C 6 H 3 NPPh 2 )C 5 H 4 N ( 11 ), 2-(2,6-Me 2 C 6 H 3 NPPh 2 )-6-MeC 5 H 4 N ( 12 ), 2-(2,6- i- Pr 2 C 6 H 3 NPPh 2 )-6-MeC 5 H 4 N ( 13 ), 2-(2,6-Me 2 C 6 H 3 NPPh 2 )-6-BnC 5 H 4 N ( 14 ), 2-(2,6- i- Pr 2 C 6 H 3 NPPh 2 )-6-BnC 5 H 4 N ( 15 ), 2-(2,6-Me 2 C 6 H 3 NPPh 2 )-6-SiMe 3 C 5 H 4 N ( 16 ), 2-(2,6- i- Pr 2 C 6 H 3 NPPh 2 )-6-SiMe 3 C 5 H 4 N ( 17 ), 2-(2,6-Me 2 C 6 H 3 NPPh 2 )-6-PhC 5 H 4 N ( 18 ), and 2-(2,6- i- Pr 2 C 6 H 3 NPPh 2 )-6-PhC 5 H 4 N ( 19 ). Attempts to oxidize the fluorinated phosphine 2-P(C 6 F 5 ) 2 -6-PhC 5 H 3 N ( 6 ) were unsuccessful. The ligand 9 reacted with PdCl 2 (PhCN) 2 to the give the square-planar, diamagnetic compound (L)PdCl 2 ( 20; L = 9 ), while the remaining ligands were used to prepare (L)NiBr 2 and (L)FeCl 2 complexes 21 − 30 and 31 − 40 (L = 10 - 19 ), respectively. In these complexes the P atoms become part of the chelate backbone. In addition, the pyridine−phosphinimines 2-(Ph 3 P NCH 2 )(C 5 H 4 N) ( 44 ), 2-(Ph 3 PNCH 2 )-6-Me(C 5 H 3 N) ( 45 ), and 2-(Ph 3 PNCH 2 )-6-Ph(C 5 H 3 N) ( 46 ) were also prepared from the reaction of 2-azidomethyl−pyridines with PPh 3 . In a similar fashion the complexes (L)PdCl 2 ( 47, 48; L = 44, 45 ), (L)NiBr 2 ( 49 − 51; L = 44 − 46 ), (L)FeCl 2 ( 52, 53 ), and (L)CoCl 2 ( 54, 55; L = 44, 45 ) were prepared. In addition, the imidazole−phosphines 1-Me-2-(PPh 2 )C 3 H 2 N 2 ( 58 ), 1-Me-2-(PPh 2 )-4,5-Ph 2 C 3 N 2 ( 59 ), and 1-Me-2-(PPh 2 )C 7 H 6 N 2 ( 60 ) were prepared and oxidized to give the imidazole−phosphinimines 1-Me-2-(2,6-Me 2 C 6 H 3 N PPh 2 )C 3 H 2 N 2 ( 61 ), 1-Me-2-(2,6- i- Pr 2 C 6 H 3 N PPh 2 )C 3 H 2 N 2 ( 62 ), 1-Me-2-(2,6-Me 2 C 6 H 3 N PPh 2 )-4,5-Ph 2 C 3 N 2 ( 63 ), 1-Me-2-(2,6- i- Pr 2 C 6 H 3 N PPh 2 )-4,5-Ph 2 C 3 N 2 ( 64 ), 1-Me-2-(2,6-Me 2 C 6 H 3 N PPh 2 )C 7 H 6 N 2 ( 65 ), 1-Me-2-(2,6- i- Pr 2 C 6 H 3 N PPh 2 )C 7 H 6 N 2 ( 66 ) and 1-Me-2-(2,6- i- Pr 2 C 6 H 3 N PPh 2 )-4-( t- Bu)C 3 HN 2 ( 67 ). Subsequent complexation afforded the species (L)PdCl 2 ( 68; L = 61 ), (L)NiBr 2 ( 69 − 75; L = 61 − 67 ), and (L)FeCl 2 ( 76 − 82; L = 61 − 67 ). Preliminary screening for activity as catalyst precursors for ethylene polymerization indicated that ethylene oligomerization may be occurring. In the case of complexes 30, 40, 74, and 82 activation with Et 2 AlCl(ClC 6 H 5 ) at 35 °C under 300 psi of ethylene effected modest catalytic dimerization of ethylene to mainly C 4 alkenes. DFT computations suggested that inclusion of P into the ligand results in diminished electrophilicity at the metal and thus a weakened ethylene−metal interaction, accounting for the modest catalytic activity. X-ray structure determinations were obtained for 2, 20, 26, 27, 35, 37, 40, 49 − 51, 54, 68, 79, and 82 .
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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 | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".