Tri- and Tetravalent and Mixed-Valence Niobium Complexes Supported by a Tripodal Tripyrrolylmethane Trianion
Bibliographic record
Abstract
The reaction of Nb 2 Cl 6 (TMEDA) 2 with the potassium salt of tripyrrolylmethane in a 1:1 ratio afforded two products which have been isolated and characterized. The first compound is the dinuclear {[HC(C 4 H 3 N) 3 ]Nb(THF)} 2 ·2THF ( 1 ), with two trivalent and diamagnetic metal centers bridged by two tripyrrolyl trianions. Each of the two ligands adopted a rather unusual bridging mode, with two rings each σ -bonding one of the two metal centers and the third both π -bonded to one of the two niobium atoms and σ -bonded to the other. The second product of the reaction is {([H(C 4 H 3 N) 3 ] 2 NbK) 2 }{Nb 4 Cl 11 [K(THF) 2 ] 2 }·2THF ( 2 ), which displays some unusual features. The complex is ionic, with the cationic {Nb 4 Cl 11 [K(THF) 2 ] 2 } 2+ unit containing the metal in a mixed-valence state. The two positive charges of the cationic moiety are balanced by two identical anionic {([HC(C 4 H 3 N) 3 ] 2 NbK) 2 } - units, each containing Nb in the tetravalent state. Each anion is connected to an identical one by the bridging potassium atom, thus assembling a linear and anionic polymeric array. A similar reaction carried out with the lithium salt of the tripyrrolide anion led instead to the simple monomeric and tetravalent complex {[HC(C 4 H 3 N) 3 ] 2 Nb}{Li(THF) 4 } 2 ( 3 ).
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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".