Transition Metal-Catalyzed Dissociation of Phosphine−Gallane Adducts: Isolation of Mechanistic Model Complexes and Heterogeneous Catalyst Poisoning Studies
Bibliographic record
Abstract
Attempts to induce the catalytic dehydrocoupling of the phosphine-gallane adduct Cy2PH.GaH3 (Cy=cyclohexyl) (1) by treatment with ca. 5 mol% of either the Rh(I) complex [{Rh(mu-Cl)(1,5-cod)}2] (cod=cyclooctadiene) or the Rh(0) species Rh/Al2O3 and [Oct4N]Cl-stabilized colloidal Rh led to catalytic P-Ga bond cleavage to generate the phosphine, H2, and Ga metal. Interestingly, subsequent treatment of the reaction mixtures with Me2NH.BH3 failed to lead to the formation of [Me2N-BH2]2 via Rh-catalyzed dehydrocoupling, which suggested that catalyst deactivation was taking place. Poisoning studies involving the treatment of the active Rh(0) catalyst with Cy2PH, PMe3, or GaH3.OEt2 showed that deactivation indeed occurred as the dehydrocoupling of Me2NH.BH3 either dramatically decreased in rate or did not take place at all. The X-ray photoelectron spectroscopy analysis of colloidal Rh(0) that had been treated with Cy2PH and PMe3 confirmed the presence of phosphorus on the catalyst surface in each case, consistent with catalyst poisoning via phosphine ligation. A mechanism for the Rh-catalyzed P-Ga bond cleavage reaction of 1 and Me3P.GaH3 (2) is proposed and involves the initial reaction of Ga-H bonds with the Rh colloid surface, which weakens and ultimately breaks the P-Ga bond. The reasonable nature of this mechanism is supported by a model reaction between the zerovalent group 9 complex Co2(CO)8 and 2 which afforded Me3P.Ga[Co(CO)4]3 (3). Consistent with the elongated and thus weakened P-Ga bond in 3, solutions of this species in Et2O subsequently form the known complex [(Me3P)Co(CO)3]2 (4) and Ga metal after 4 h at 25 degrees C.
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How this classification was reachedexpand
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 | 0.000 |
| 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) | 0.000 | 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 teacher head, 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".