Pyridine− and Imidazole−Phosphinimine Bidentate Ligand Complexes: Considerations for Ethylene Oligomerization Catalysts
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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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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 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 it