Solution and Solid-State Characteristics of Imine Adducts with Tris(pentafluorophenyl)borane
Bibliographic record
Abstract
Adducts of the N -benzyl imines Ph(R)C NBn (R = Ph, CH 3, H) and t Bu(CH 3 )C NBn and the N -phenyl imine Ph(H)C NPh with the Lewis acid tris(pentafluorophenyl)borane, B(C 6 F 5 ) 3, have been prepared and characterized in solution and in the solid state. For each imine, the Lewis acid is N-bound, with the exception of the sterically demanding base t Bu(CH 3 )C NBn, which reacts with B(C 6 F 5 ) 3 through its enamine tautomer to form an α-C bound adduct, 5 . In the N-bound imine−borane adducts 1 − 4, steric crowding and π-stacking between C 6 F 5 and C 6 H 5 rings results in restricted rotation about the B−N and B−C bonds; the dynamic behavior which results can be studied using variable-temperature 19 F and 1 H NMR spectroscopy. For the unsymmetrical ketimines and aldimines, kinetic adducts of the thermodynamically dominant free imine are observed to form initially upon treatment with B(C 6 F 5 ) 3; these adducts slowly convert thermally to the thermodynamic adducts of the less stable imine. For the ketimine Ph(CH 3 )C NBn, both the kinetic adduct 2-k and the thermodynamic adduct 2-t were fully characterized. In the solid-state structures of all the adducts except 5, one or two C 6 F 5 /C 6 H 5 stacking interactions are present; in one case, the adduct 3-t between B(C 6 F 5 ) 3 and Ph(H)C NBn, intermolecular stacking interactions are apparent in the crystal-packing diagram. The implications of the structures of these adducts for Lewis acid mediated addition of nucleophiles to imines is discussed.
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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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".