Macrocyclic Complexes of Niobium(III): Synthesis, Structure, and Magnetic Behavior of Mononuclear and Dinuclear Species That Incorporate the [P<sub>2</sub>N<sub>2</sub>] System
Bibliographic record
Abstract
The coordination chemistry of the two mixed donor macrocyclic ligands R [P 2 N 2 ] (where R [P 2 N 2 ] = RP(CH 2 SiMe 2 NSiMe 2 CH 2 ) 2 PR, R = cyclohexyl (Cy) or phenyl (Ph)) with niobium(III) is presented. The reaction of the dilithio precursors R [P 2 N 2 ]Li 2 (S) (R = Cy, S = THF; R = Ph, S = 1,4-dioxane) with NbCl 3 (DME) (DME = 1,2-dimethoxyethane) generates the complexes R [P 2 N 2 ]NbCl (R = Cy, 1; R = Ph, 2 ). For R = Cy, single-crystal X-ray diffraction studies and variable-temperature magnetic susceptibility measurements indicate that 1 is mononuclear in the solid state; however, analogous variable-temperature magnetic data suggest that 2 is dinuclear in the solid state due to the observation of antiferromagnetic exchange. In solution, 2 is apparently monomeric similar to 1 . Adduct formation between these mononuclear complexes is also evident; reaction of 2 with neutral donors and coordinating solvents produces the mononuclear derivatives Ph [P 2 N 2 ]NbCl(L) (L = py, CO, PMe 3, THF, MeCN), of which the pyridine adduct, 3e, has been characterized crystallographically. Subsequent replacement of the chlorides can be achieved to generate the paramagnetic alkyl complexes R [P 2 N 2 ]NbR‘ (R = Cy, Ph; R‘ = CH 2 SiMe 3, CH(SiMe 3 ) 2 ). The representative compounds Cy [P 2 N 2 ]NbCH 2 SiMe 3 ( 4a ) and Ph [P 2 N 2 ]NbCH(SiMe 3 ) 2 ( 5b ) have been characterized by X-ray crystallography.
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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".