Chemical Properties of the Pd<sub>4</sub>(dppm)<sub>4</sub>(H)<sub>2</sub><sup>2+</sup> Cluster and the Homogeneous Electrocatalytical Behavior of Hydrogen Evolution and Formate Decomposition
Bibliographic record
Abstract
Two new reductive electrochemical (CO2 + H2O + 2e-; HCO2H + 2e-) and two new chemical methods (Al(CH3)3 + proton donor; NaO2CH) to prepare the title compound from Pd2(dppm)2Cl2 are reported. For the latter method, an intermediate species formulated as Pd2(dppm)4(O2CH)2(2+) is identified spectroscopically (1H NMR, 31P NMR, IR, and FAB-MS). Limited stability of the title compound in the presence of Cl- and Br- as counteranions is noticed and is due to sensitivity of the cluster toward nucleophilic attack of the halide ions. This result is corroborated by the rapid decomposition of these clusters in the presence of CN- to form the binuclear species Pd2(dppm)2(CN)4 and by the preparation of the stable salts [Pd4(dppm)4(H)2](X)2(X- = BF4-, PF6-, BPh4-). Upon a two-electron electrochemical reduction of this cluster to the neutral species (E1/2 = -1.42 V vs SCE in DMF) in the presence of 1 equiv of HCO2H, a highly reactive species formulated as [Pd4(dppm)4(H)3]+ is generated and characterized by 1H NMR, 31P NMR, and cyclic voltammetry. Subsequent addition of H+ (via RCO2H; R = H, CH3, CF3, C6H5) under the same reducing conditions, induces the homogeneous catalysis of H2 evolution. The turnover number is found to be 134 in 2 h, with no evidence for catalyst decomposition. This same species also exhibits a one-electron oxidation process (E1/2 = -0.61 V vs SCE in DMF) that induces the catalytical decomposition of formate (HCO2- --> CO2 + 1/2H2 + 1e-). This double catalysis from the same cluster intermediate is unprecedented.
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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 | 0.000 |
| 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".