Highly Reactive Uranium(III) Polypyrrolide Complexes: Intramolecular C−H Bond Activation, Ligand Isomerization, and Solvent Deoxygenation and Fragmentation
Bibliographic record
Abstract
The reaction of UX 3 (THF) 4 (X = Cl, I) with the tetraanion of {[(−CH 2 −) 5 ] 4 -calix[4]tetrapyrrole} gave different compounds depending on the uranium halide, the alkali-metal cation (Li vs K), the stoichiometric ratio of ligand to uranium, and the solvent used. Reaction of the potassium salt of the ligand with uranium iodide in THF and in the ratio 1:1 afforded the dinuclear, tetravalent species {[{[(−CH 2 −) 5 ] 4 -calix[4]tetrapyrrole}UK(THF) 3 ] 2 (μ 2 -O)}·2THF ( 1 ). The source of the bridging oxygen atom is a THF deoxygenation process. A reaction carried out under identical conditions but with the tetralithium salt of the calix[4]tetrapyrrole afforded instead intractable material unless a stoichiometric ratio of two ligands per uranium was employed. In this event, a new species, the dinuclear tetravalent species [{[(−CH 2 −) 5 ] 4 -calix[4]pyrrole}ULi(THF) 2 ] 2 ·hexane ( 2 ), was isolated. In this complex, the β-C atom of one of the pyrrole rings of the macrocycle was deprotonated and metalated by uranium of a second identical unit, thus assembling the dinuclear structure. The reaction is not accompanied by loss of hydrogen gas, while the excess ligand is acting as a Brønsted base. An identical reaction carried out by using uranium trichloride afforded instead the mononuclear tetravalent species ({[(−CH 2 −) 5 ] 4 -calix[4]tetrapyrrole}ULi(OC 2 H 5 )(THF) 2 ) ( 3 ). In this compound one pyrrole ring was isomerized by shifting the attachment of the chain from the α- to the β-position. The LiOCH 2 CH 3 unit was generated by another pathway of THF fragmentation. Finally, a reaction carried out in dimethoxyethane with the purpose of preventing oxidative attack to the metal center, afforded the mononuclear trivalent complex [{[(−CH 2 −) 5 ] 4 -calix[4]tetrapyrrole}U(DME)][K(DME)] ( 4 ).
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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) | 0.001 | 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 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".