Lewis acid-base interactions in the synthesis of titanium phosphinimide cations.
Bibliographic record
Abstract
The active species Cp(NPtBu3)TiMe(mu-MeB(C 6F5)4) and [Cp(NPtBu3)TiMe] [B(C6F5)4], generated by the reaction of Cp(NPtBu3)TiMe2 with the activators B(C 6F5)3 and [C(C6H5) 3][B(C6F5)4], are thought to be the active species in olefin polymerization processes. Both species have been stabilized by the coordination of Lewis bases, pyridines (Py, 4-EtPy, 4- tBuPy, and 4-DMAP) and tertiary phosphines (PMe3, PnBu 3, P(C6H5)3, P(p-CH 3C6H4)3). The use of such Lewis bases allowed for the isolation and characterization of ion pair complexes of the general formula [Cp(NPtBu3)TiMe·LB] [RB(C 6F5)3] (LB = Lewis base; R = Me, C6F 5). These reactions show a dependency on the steric properties of the Lewis base. The use of sterically bulky tertiary phosphines (P(o-CH 3C6H4)3, PiPr3 , PCy3 and PtBu3) demonstrated this dependency, affording unexpected phosphonium salts as products. The role of the reaction solvent (dichloromethane and chlorobenzene) is evaluated in these reactions. Dichloromethane reacts with the reagents (active titanium complexes and Lewis bases), promoting the formation of unexpected products (some of these species are characterized). However, chlorobenzene allows a better control of the reactions between the activated complex and Lewis bases. The dimerization products [{Cp(NPtBu3)TiMe} 2(mu-Cl)] [RB(C6F5)3] (R = Me, C 6F5) (2.18), [{Cp(NPtBu 3)Ti(mu-Cl)2}][RB(C6F5)3] 2 (2.21) and [{Cp(NPtBu3)TiMe} 2(mu-Me)] [RB(C6F5)3] (2.23 ) of the cationic moiety of the active complexes [Cp(NPtBu 3)TiMe]+ showed also to be dependent on the reaction conditions and solvent. Reactions of Lewis acids (B(C6F5)3 and [C(C6H5)3][B(C6F5) 4] with Lewis bases (substituted pyridines and tertiary phosphines) are also described. A similarity in reactivity between B(C 6F5)3 and the trityl carbocation is observed, as the products afforded from these reactions are analogous. Reactions of Lewis acids and Lewis bases were found to be related to the steric bulk associated with the Lewis base in conjunction with the solvent, CH2Cl 2.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .C33. Source: Masters Abstracts International, Volume: 43-01, page: 0216. Adviser: Douglas W. Stephan. Thesis (M.Sc.)--University of Windsor (Canada), 2004.
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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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".