Oxidative Addition of Ethyl Iodide to a Dimethylplatinum(II) Complex: Unusually Large Kinetic Isotope Effects and Their Transition-State Implications
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Bibliographic record
Abstract
The mechanism of oxidative addition of ethyl iodide to [PtMe 2 (2,2′-bipyridine)], 1, has been investigated by product analysis and by study of secondary deuterium kinetic isotope effects (KIEs), using the reagents C 2 H 5 I, C 2 D 5 I, CH 3 CD 2 I, and CD 3 CH 2 I. The reactions in acetone and benzene give [PtIMe 2 Et(bipy)], mostly as the product of trans oxidative addition, but with some of the isomeric product of cis oxidative addition and some [PtIMe 3 (bipy)], resulting from methyl group transfer. The reaction in benzene is light-sensitive, giving additional major products [PtI 2 Me 2 (bipy)] and [PtIMe 2 (OOEt)(bipy)], as well as several minor products indicative of a photochemically initiated free-radical reaction. No H/D exchange within the ethyl group was observed in any of the products. The dark reactions in acetone and benzene follow second-order kinetics, with large negative values of the entropy of activation, indicating the S N 2 mechanism of oxidative addition of ethyl iodide to 1 . However, for reaction with C 2 H 5 I vs C 2 D 5 I, values of the KIE k H / k D range from 1.32 to 1.72 in acetone and from 1.44 to 1.90 in benzene solution, and studies with CH 3 CD 2 I and CD 3 CH 2 I show that α- and β-deuterium KIEs make about equal contributions to the overall KIE. These are the first reports of isotope effects on the rate of oxidative addition reactions of ethyl halides, and the high values of the secondary deuterium KIE were unexpected for the S N 2 mechanism. Possible reasons for these observations are discussed.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| 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) | 0.004 | 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 it