The poisonous truth about the mercury drop test: the effect of elemental mercury on Pd(0) and Pd(II)ArX intermediates
Bibliographic record
Abstract
The mercury drop test is a widely used method for distinguishing between homogeneous and heterogeneous catalysis in organometallic systems. However, recent research has highlighted the limitations of this test due to the intrinsic reactivity of some organometallic compounds towards elemental mercury. In this study, we used real-time mass spectrometry with charge-tagged substrates to investigate the effect of elemental mercury on LnPd0 and PdIIArX intermediates common in palladium-catalysed cross-coupling reactions. Our findings demonstrate that mercury can interact with both species through redox-transmetallation and amalgamation processes, leading to a decrease in catalytic activity. This result further calls into question the fundamental assumption of mercury selectivity towards heterogeneous catalytic species. These results highlight the importance of careful consideration of the results the mercury drop test provides and encourages further research to gain a more comprehensive understanding of catalyst poisoning mechanisms.
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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 | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.001 | 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".