Evaluating 1,1′-Bis(phosphino)ferrocene Ancillary Ligand Variants in the Nickel-Catalyzed C–N Cross-Coupling of (Hetero)aryl Chlorides
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Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide Previous reports in the literature have established the utility of 1,1′-bis(diphenylphosphino)ferrocene (DPPF, L Ph ) in the nickel-catalyzed cross-coupling of (hetero)aryl electrophiles with primary or secondary amines. In an effort to evaluate the effect of varying the PR 2 -donor groups on catalytic performance in such transformations, a series of 10 structurally varied 1,1′-bis(bis(alkyl/aryl)phosphino)ferrocene ancillary ligands ( L X ) were systematically examined in selected competitive test cross-couplings of (hetero)aryl halides with furfurylamine, morpholine, and indole employing Ni(COD) 2 / L X catalyst mixtures. In addition to the excellent performance observed for the parent ligand L Ph in a number of the test transformations explored, selected dialkylphosphino (e.g., DiPPF, L i Pr ) and meta-disubstituted diarylphosphino variants of L Ph also proved highly effective. In particular, the electron-deficient ligand variant L CF3 featuring 3,5-bis(trifluoromethyl)phenyl groups on phosphorus was found to exhibit superior catalytic performance relative to L Ph in most of the test transformations involving the N-arylation of indole. Our efforts to prepare Ni(II) precatalysts of the type ( L X )Ni( o -tolyl)Cl, in analogy with known ( L Ph )Ni( o -tolyl)Cl, by employing several literature methods met with mixed results. Whereas ( L i Pr )Ni( o -tolyl)Cl was prepared straightforwardly and was crystallographically characterized, the use of L CF3 or ligands featuring tert- butyl ( L t Bu ), o -tolyl ( L o- tol ), or 4-methoxy-3,5-dimethylphenyl ( L OMe ) groups on phosphorus under similar conditions resulted in poor conversion to product and/or the formation of poorly soluble materials, highlighting the limitations of this commonly used precatalyst design.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 it