Heavier Main Group Dimetallene Reactivity: Effects of Frontier Orbital Symmetry
Bibliographic record
Abstract
The major theme of this review concerns the reaction pathways of heavier main group 13 dimetallenes with olefins, cyclic olefins, polyolefins, other unsaturated molecules, and hydrogen. For gallium derivatives, these reactions proceed readily in high yield under ambient conditions. Early investigations showed that the group 13 dimetallenes dissociated to one-coordinate metallanediyl monomers, which suggested that they reacted as monomeric species due to their more open, less hindered structures. However, recent DFT calculations by Tuononen and co-workers show that the reaction of the monomers with olefins or hydrogen involves very large energy barriers and that the dimetallenes react instead as undissociated dimers. In contrast to the corresponding all-carbon systems, where [2 + 2] cycloadditions are forbidden because of π–π* symmetry mismatch, the dimetallenes react with olefins via two stepwise, symmetry-allowed [2 + 2] cycloadditions to give 1,4-digallacyclohexanes. The addition of the H 2 proceeds by a different mechanism, initially involving a 1,2-dihydride intermediate to ultimately yield two ArGaH 2 molecules, which recombine to give Ar(H)Ga(μ-H) 2 Ga(H)Ar. The corresponding dialuminene is more highly reactive and reacts with solvent toluene to give an unusual [2 + 4] cycloaddition product. Calculations reveal that there is an enhanced diradical character in its bonding and that the reaction with propene affords an open-shell transition state involving a dangling CH 3 ĊHCH 2 Al moiety with unpaired spin density also on aluminum.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".