Cobalt Complexes Containing Dimethyldihydropyrene-Substituted Cyclobutadiene Ligands
Bibliographic record
Abstract
CpCo(CO) 2 -induced cyclization of the dihydropyrenyl methyl acetylene 12 selectively gave cis (head to head) cyclobutadiene (Cbd) cobalt Cp complexes, 15, in 64% yield as a mixture of three isomers, which differ in the orientation of the internal DHP methyl substituents with respect to the CoCp unit. Cyclization of the ester-substituted alkyne 13 likewise gave three cis isomers of 16 in 30% yield. The bis-DHP substituted alkyne 9, however, gave 50% of a mixture of cis and trans (head to tail) isomers of 17 . An X-ray crystal structure for complex 15 showed exclusively the cis regioisomer; however, the CpCo fragment was disordered over two main sites in a 56:41 ratio and the internal methyl groups were also disordered with respect to the CoCp unit. These two major sites are related by an approximately 180° rotation of the CpCo(Cbd) unit around the edge of the Cbd ring bearing the two DHP substituents. The aromaticity of the cyclobutadiene cobalt fragment was studied by examination of the DHP internal methyl chemical shifts, coupling constants, and bond distance alternation. Comparison of the 3 J 9′,10′ values for complex 16 and the phenyl derivative 5 and the sum of the bond length deviations from average for complexes 15 and 5 are consistent with the idea that, quantitatively, the aromaticity of the cyclobutadiene cobalt fragment is on the same order as that of benzene. Study of the photoopening of the naphthoyl dihydropyrene cobalt complex 26 indicated that the organometallic fragment slowed the reaction by about 12 times relative to the precursor, alkyne 25 .
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".