Influence of Different Ligands X<sup>-</sup> (X = F, Cl, Br, I, NO<sub>2</sub>, CN) on the Rate and Mechanism for Methane Activation by PtCl<sub>2</sub>X<sub>2</sub> in Aqueous Solution. A Density Functional Theory Study
Bibliographic record
Abstract
A density functional study has been carried out on catalytic methane activation by a 1:2 molar mixture of PtCl 2 (H 2 O) 2 and X - with X = none, F, Cl, Br, I, NO 2, CN. The objective of this study was to better understand the original Shilov experiments, for which a detailed characterization of the active species and the rate determining step has been difficult experimentally. We have found that the rate-determining step for all mixtures is methane uptake rather than C−H activation. Our calculations indicate further that the active species for the weakly coordinating ligands X - = Cl -, Br -, I - are trans -PtCl 2 X(H 2 O) - and cis -PtX 2 Cl(H 2 O) -, whereas the most abundant complex PtCl 2 X 2 2- and other species with only halogens have no noticeable activity. For the more strongly coordinating ligands X - = F -, NO 2 -, CN -, the most abundant species are PtCl 2 (H 2 O) 2, PtCl 2 X(H 2 O) -, PtClX 2 (H 2 O) -, PtX 4 2-, and PtClX 3 - . Of these species only cis -PtCl 2 (H 2 O) 2 and cis -PtCl 2 X(H 2 O) - are active catalysts for H + /D + exchange. For all the species formed, the free energy barriers of methane and C−H activation have been reported, along with their energy of formation relative to cis -PtCl 2 (H 2 O) 2 and X - .
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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 | 0.001 |
| 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".