Mechanistic insight into cooperative catalysis with pentanuclear nickel clusters: catalytic alkene dimerization and silyl-silylene and silylyne clusters.
Bibliographic record
Abstract
This work gives structural insights into potential intermediates relevant to the mechanism of stereoselective catalysis by pentanuclear Ni complexes, such as the previously reported stereoselective dimerization of norbornene to the C2 symmetric (Z) anti-(bis-2,2'-norbornylidene) by [(iPr3P)Ni]5H6 (1). Attempts to generate a polymer by reaction of norbornadiene with catalytic 1 instead selectivity gave the exo-trans-exo 2+2 cyclodimerized product, 1,4,4a,4b,5,8,8a,8b-octahydro-1,4:5,8-dimethanobiphenylene. The reaction of cyclopentene with catalytic [(iPr3P)Ni]5H6 (1) gave a mixture of 1,1'-bi(cyclopentylidene) and 1-cyclopentylcyclopentene as organic products. Catalysis terminated when 1 was fully converted to the twisted trapezoidal pentanuclear cluster (iPr3P)4Ni5(C10H13)H5 (2). Complex 2 reacted with H2 to give back 1. Attempts to functionalize the organic fragment in 2 with diphenylsilane instead gave (iPr3P)4Ni5(SiPh2)(SiPh2H)H5 (3), which retains the twisted trapezoidal geometry. Complex 3 was also prepared by direct reaction of Ph2SiH2 with 1. Triethylsilane reacts with 1 to give a new distorted pentagonal cluster [(iPr3P)Ni]5(μ5-SiEt)H7 (4) from Si‒H and multiple Si‒C bond cleavages. The new structures demonstrate the remarkable flexibility in the geometry of the persistent Ni5 core and provide insight into the structures of intermediates in the reactions with [(iPr3P)Ni]5H6.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".