Effect of Azide and Chloride Binding to Diamino-bis(phenolate) Chromium Complexes on CO<sub>2</sub>/Cyclohexene Oxide Copolymerization
Bibliographic record
Abstract
The affinity for nucleophile (azide, N3–, and chloride, Cl–) binding significantly influences the catalytic activity of chromium complexes for the copolymerization of cyclohexene oxide (CHO) and CO2. The binding of N3– and Cl– to two amino-bis(phenolate) Cr(III) chloride complexes [L1Cr(μ-Cl)]2 (1) and [L2CrCl(THF)] (2·THF), where L1 = methoxyethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenolate) and L2 = dimethylaminoethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenolate), were studied by both matrix assisted laser desorption/ionization time-of-flight and electrospray ionization mass spectrometry (MALDI-TOF-MS and ESI-MS, respectively). Upon reaction with [PPN][N3] ([PPN] = bis(triphenylphosphine)iminium), 1 exhibited greater ability to form six-coordinate bis-azide ions [L1Cr(N3)2]− and produced fewer five-coordinate species detected by MS than 2·THF. This corresponded to 2·THF having a significantly faster rate of polymerization with anionic nucleophile cocatalysts than 1. In the presence of 1 equiv of [PPN][N3], 1 showed a slow reaction rate with an induction period of 20 min, whereas 2·THF showed a much faster reaction rate with no induction period. Also, 1 in the presence of 1 equiv of [PPN][Cl] showed faster copolymerization than in the presence of 2 equiv of [PPN][Cl]. The binding of chloride to 1 from addition of [PPN][Cl] was studied by UV–vis spectroscopy, which showed an equilibrium constant of 1.6 × 103 M–1 favoring the formation of [L1Cr(Cl)2]−. The ring-opening process of CHO was observed in the mixture of 2·THF/CHO/[PPN][N3] via ESI-MS. Combined with MALDI-TOF-MS of the polymer product obtained within the first 60 min, it was shown that N3– preferentially initiates ring-opening of the epoxide in CHO. Upon consumption of N3– through generation of active polymer chains, the chloride originating from the metal complex can serve as initiator of epoxide ring-opening. This was confirmed by the occurrence of chloride-containing polymers later in the reaction. Taken together, these studies provide mechanistic insight into the copolymerization of CO2 and epoxide by diamino-bis(phenolate) Cr(III) chloride complexes.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".