Supra–Supra, Supra–Antara, and Stepwise-Diradical Pathways for an Observed 16-Electron Double-[4 + 4] Cycloaddition within Metal-Templated Dialkyne Dimers (PtX<sub>2</sub>)<sub>2</sub>(μ-R<sub>2</sub>PCCCCPR<sub>2</sub>)<sub>2</sub>
Bibliographic record
Abstract
Quantum chemistry calculations are used to provide insight into the cycloaddition of two dialkyne chains in initially monocyclic organoplatinum dimers of the type (PtX(2))(2)(μ-R(2)PC(4)PR(2))(2), where X = Cl or Me and R = Ph or Me. Previous experimental studies showed that the cycloaddition occurs with {X, R} = {Cl, Ph} but not {Me, Ph}. Two concerted pericyclic paths, a D(2h)-symmetry double-[π4s+π4s] "Hückel path" and a D(2)-symmetry double-[π4s+π4a] "Möbius path", were explored via orbital energy correlation diagrams (OECDs) computed using a singly occupied molecular orbital technique developed earlier. In accord with pericyclic reaction theory, the 16e(-) rearrangement is forbidden along the D(2h) Hückel path; four electrons would need to change their orbital symmetries. The D(2) Möbius path, afforded by the natural twist in the reactant structure which allows the desired Möbius orbital connectivity for a 4n rearrangement, is concluded to be a borderline forbidden pathway. This Möbius path creates avoided crossings in the OECD, which allows consistent orbital populations throughout the reaction, but it does not cause a change in intended orbital correlation, and the predicted activation barrier is rather high (∼50 kcal mol(-1)). The avoided crossings show strong coupling, but a clear HOMO-LUMO gap for the reaction is not produced. A stepwise path is also presented, with evidence of its diradical character.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 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".