Syntheses and Characterization of Upper Rim 1,2- and 1,3-Diphosphinated Calix[4]arenes and Their Corresponding 1,5-Cyclooctadienylrhodium(I) Complexes: Comparison of the Catalytic Hydroformylation Properties of Terminal Alkenes
Bibliographic record
Abstract
The 5,11- (1,2-isomer) and 5,17-bis(dialkylphosphino)-25,26,27,28-tetra- n -propoxycalix[4]arene (1,3-isomer) ligands (alkyl = Me, i- Pr) have been prepared and coordinated to Rh(COD) + fragments (COD = 1,5-cyclooctadiene). The ligands 5,17-bis(diphenylphosphino)-11,23-dibromo-25,26,27,28-tetra- n -propoxycalix[4]arene and 5,11-bis(diphenylphosphino)-25,26,27,28-tetra- n -propoxycalix[4]arene have been coordinated to M(COD) + (M = Rh, Ir) and RhCl(CO) fragments, as well. On the basis of mass spectrometry and 31 P NMR spin−lattice relaxation time measurements ( T 1 ), all of the complexes are found to be dimers. Molecular modeling provides evidence that ring stress favors the dimer over the monomer, and the modeled structures for both 1,2- and 1,3-isomers have been corroborated by the comparison of the photophysics of the Ir(COD) + species at 77 K. The decrease in emission lifetimes of the P 2 Ir(C C) 2 + lumophore in the presence of 1-hexene is more pronounced for the 1,3-isomer, indicating reduced steric hindrance about the metallic center. The catalytic hydroformylation of five terminal alkenes using all six Rh(COD) + catalyst precursors has been investigated under various conditions in order to extract the turnover frequencies (tof as defined as the number of moles of products divided by the total number of moles of rhodium used per hour) and the ratios of the product distribution ( n/ i, normal vs internal). The comparison of the data suggests that the basicity and the cone angle of the phosphines influence the n/i ratios. The tof's are generally larger for the 1,2-series for 1-hexene, but depend on the nature of the phosphine for styrene, vinyl acetate, vinyl benzoate, and vinyl p-tert -butylbenzoate. All in all, these complexes are good catalysts with respect to literature data, notably those containing the ( i -Pr 2 P)− groups. During the course of this study, one hydride carbonyl complex has been synthesized and characterized from 1 H and 31 P NMR, IR, and T 1 measurements.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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".