Attempting to Reduce the Irreducible: Preparation of a Rare Paramagnetic Thorium Species
Bibliographic record
Abstract
A bis-pyrrolide ligand containing a nonconjugated aromatic ring in the backbone was reacted with ThCl 4 (DME) 2, affording the corresponding η 6 -{1,3-[(2-C 4 H 3 N)(CH 3 ) 2 C] 2 C 6 H 4 }ThCl 3 ][Li(DME) 3 ] ( 1 ) complex. In this species, the π-bonding interaction of the actinide with the ring is probably induced by steric constraint. The bonding mode of the pyrrolide rings was switched from σ to π upon treatment of complex 1 with Et 3 Al. This reaction was also accompanied by deprotonation of the aromatic ring and formation of two similar compounds with the ring σ-bonded to the Th metal center. The two compounds {[{1,3-[(η 5 -2-C 4 H 3 N)(CH 3 ) 2 C] 2 C 6 H 4 }Th(μ-Cl-AlEt 2 ) 2 ](μ-Cl) 2 [{1,3-[(η 5 -2-C 4 H 3 N)(CH 3 ) 2 C]C 6 H 4 }Th] (μ-AlEt 2 )Cl]}·(C 7 H 8 ) 0.5 ( 2a ) and {[{1,3-[(η 5 -2-C 4 H 3 N)(CH 3 ) 2 C] 2 C 6 H 4 }ThCl(μ-Cl) 2 [Li(DME)] 2 ( 2b ) were isolated and fully characterized. The common feature among these two species is that the switching of bonding mode of the pyrrolide rings, resulting from the coordination of the aluminum residues, is accompanied by deprotonation of the central ring. Attempts to reduce 1 yielded the paramagnetic [{η 5 -1,3-[(η 5 -2-C 4 H 3 N)(CH 3 ) 2 C] 2 C 6 H 4 }ThK(μ-Cl) 3 ][Li(DME) 3 ] ( 3 ), which on the basis of the connectivity might be regarded as a rare case of Th(III). However, DFT calculation have elucidated the electronic structure of this species, which should be regarded as containing tetravalent Th bonded to the ligand radical anion. The spin density is mainly localized at the ring C atom, which is deformed and deviates from the planarity. Similar reductions carried out under slightly different reaction conditions afforded {η 6 -1,3-[(2-C 4 H 3 N)(CH 3 ) 2 C] 2 C 6 H 4 }Th{μ-η 5 -1,3-[(η 5 -2-C 4 H 3 N)(CH 3 ) 2 C] 2 C 6 H 5 }K(DME) 2 ( 4 ). In this complex the metal is surrounded by two ligands, one of which appears as having been partly hydrogenated at the central aromatic ring. Treatment of an in situ generated transient low-valent species with azobenzene as mild oxidizing agent resulted in reoxidation to a tetravalent thorium diphenylhydrazido species, [{η 6 -1,3-[(η 5 -2-C 4 H 3 N)(CH 3 ) 2 C] 2 C 6 H 4 }Th(μ - η 2 -PhNNPh)(μ-Cl)(Cl)Li(DME)][Li(DME) 3 ] ( 5 ).
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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 | 0.001 | 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".