Preparation of an Active Neodymium Catalyst for Regioselective Butadiene<i>cis</i>-Polymerization Supported by a Dianionic Modification of the 2,6-Diiminopyridine Ligand
Bibliographic record
Abstract
Treatment of the 2,6-diiminopyridine ligand 2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N C(CH 3 )} 2 (C 5 H 3 N) with 2 equiv of Me 3 SiCH 2 Li afforded the corresponding {[2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N-C (CH 2 )} 2 (C 5 H 3 N)] 2 - ( 1 ) dianion via deprotonation of the two methyl groups attached to the two imine functions. Reaction of 1 with NdCl 3 (THF) 3 yielded {[2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N-C (CH 2 )} 2 (C 5 H 3 N)]Nd(THF)}(μ-Cl) 2 [Li(THF) 2 ]·0.5(hexane) ( 2a ), whose recrystallization from DME gave the corresponding ionic {[2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N-C (CH 2 )} 2 (C 5 H 3 N)]NdCl 2 (DME)}{Li(DME) 3 ]( 2b ). With the exception of the reaction with (allyl)MgBr, which proceeded readily with 2b to form the allyl derivative {[2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N-C (CH 2 )} 2 (C 5 H 3 N)]Nd(η 3 -C 3 H 5 )Br}{Li(DME) 3 } ( 3 ), compounds 2a, b are not suitable starting substrates for further alkylation reactions. A viable synthetic strategy for the preparation of alkyl derivatives of 2 consisted instead of the pretreatment of NdCl 3 (THF) 3 with RLi [R = Me 3 SiCH 2, CH 3 ] at low T followed by treatment with either the diimine ligand or 1 . According to this procedure, the terminally bound alkyl derivative [2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N-C (CH 2 )} 2 (C 5 H 3 N)]Nd[CH 2 Si (CH 3 ) 3 ](THF) ( 4 ) was prepared and subsequently crystallographically characterized. The same synthetic procedure with MeLi afforded {[2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N-C (CH 2 )} 2 (C 5 H 3 N)]Nd}(μ-CH 3 ) 2 [Li(THF) 2 ] ( 5 ) and {[2,6-{[2,6-(i-Pr) 2 C 6 H 3 ]N-C (CH 2 )} 2 (C 5 H 3 N)]Nd}(μ-Cl)(μ-X)[Li (THF) 2 ] ( 6 ) [X = Cl 53%, Me 47%] depending on the MeLi/Nd ratio. Both 5 and 6 as well as 2a are potent catalysts for the cis -polymerization of butadiene.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.000 | 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 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".