Influence of Cis and Trans Ligands in Platinum(II) Complexes on the Ability of the Platinum Center to Activate C−H Bonds. A Density Functional Theory Study
Bibliographic record
Abstract
We have studied the influence of different ligands X (X = F, Cl, Br, I, NO 2, and CN) on the C−H bond activation of CH 4 in trans -PtCl 2 X(CH 4 ) −, 1, and trans -PtClX 2 (CH 4 ) −, 2, where X is either trans ( 1 ) or cis ( 2 ) to methane. For 1 with X in the trans position, the trans -PtCl 2 X − fragment interacts with CH 4 through the overlap between the empty d σ -based orbital 2a 1 pointing along the Pt−X direction and σ CH on CH 4 . An interaction also takes place between an occupied d σ -based orbital 1b 1 and the empty σ* CH orbital on CH 4, where the d π metal orbital is positioned perpendicular to the PtCl 2 X − plane. The d σ metal orbital contribution in 2a 1 is antibonding with respect to σ x on X, whereas d π in 1b 1 is antibonding with respect to π x . Through the series F, Cl, Br, I, NO 2, and CN, the energies of σ x and π x increase. This is mostly an electronegativity effect. The increase in energy causes an increase in the contribution from σ x and π x to 2a 1 and 1b 1, respectively. As a consequence, the bonding overlaps and will diminish, as only the d-component in 2a 1 and 1b 1 contributes to the overlap. As a result of the decreasing bonding overlaps, the Pt−CH 4 bond strength will decline. It is thus shown that the experimentally established order of trans-labilizing power for the series of ligands X studied here, F < Cl < Br < I < NO 2 < CN, can be related to the orbital energies of σ x and π x and the electronegativity of the elements that are involved in these orbitals. The labilization of the Pt−CH 4 bond in the C−H activation transition state is even larger than in the adduct 1, leading to an increase in the C−H activation barrier along the series F < Cl < Br < I < NO 2 < CN. For 2 with X in the cis position, solvation has the largest influence on trends in the Pt−CH 4 bond for both 2 and the transition state. However C−H activation barriers are quite similar for different 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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".