Substitution reactions at the Ni(III) cation in macrobicyclic complexes Reaction of metal ion complexes prepared from ligands L<sup>1</sup> (17-oxa-1,4,8,11-tetraazabicyclo[6.5.6]nonadecane) and L<sup>2</sup> (17-oxa-1,4,8,11-tetraazabicyclo[10.5.2]nonadecane) with chloride ion
Bibliographic record
Abstract
The potentially penta-coordinating ligand L1 has been synthesized by reaction of the bridge bis-(2-(methylsulfonyl)oxyethyl)ether with the tetraazamacrocycle cyclam (cyclam = 1,4,8,11-tetraazatetradecane). The copper(II) complex was characterized initially and subsequent demetallation provided pure L1. Electrochemical and chemical oxidation of the nickel(II) species yields a Ni(III) ion (low-spin d7, rhombic, gxx 2.195, gyy 2.189, gzz 2.027) of sufficient stability in acidic solutions for kinetic measurements to be undertaken of substitution reactions at the sixth site. The isomeric ligand L2, has been synthesized previously, and reactions of the [Ni(L1)(solv)]3+ and [Ni(L2)(solv)]3+ ions with chloride have also been investigated. In both reactions, an unusually high acid dissociation constant is observed, associated with the proposed replacement of the apical ether oxygen by a water molecule that is bound both to the metal centre and hydrogen bonded to the ether. The structure [Ni(L2)](PF6)2 (monoclinic, P21/c, a = 10.699(2), b = 13.244(4), c = 16.603(2) Å, β = 92.10(1)°) converged at R = 0.055 (R' = 0.057) for 325 parameters using 3293 reflections with I > 2σ(I). In this complex, the detachment of the ether O donor to yield a square-planar complex is confirmed. Comparisons are made with substitution rates at other Ni(III) macrocyclic ions.Key words: nickel(III), substitution, macrobicyclic ligand, synthesis, kinetics.
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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".