Dialkyl and Trialkyl Heterobinuclear Complexes of Rhodium and Iridium: Models for Adjacent-Metal Involvement in Bimetallic Catalysts
Bibliographic record
Abstract
The heterobinuclear dialkyl complexes [RhIr(R) 2 (μ-CO)(dppm) 2 ] (dppm = μ-Ph 2 PCH 2 PPh 2; R = CH 3 ( 2 ), CH 2 Ph ( 3 )) have been prepared. Both A-frame-like compounds have one alkyl group terminally bound to each metal and a bridging carbonyl ligand. Some subsequent reactivity studies of 2 are reported. Reaction of 2 with CO yields [RhIr(CO) 3 (dppm) 2 ] and acetone. If this reaction is monitored at low temperature by NMR spectroscopy, the dicarbonyl species [RhIr(CH 3 ) 2 (CO) 2 (dppm) 2 ] ( 4 ) is first observed, followed by [RhIr(CH 3 ) 2 (CO) 3 (dppm) 2 ] ( 5 ). In both products, both methyl groups are bound to Ir. Warming to ambient temperature under CO yields acetone and [RhIr(CO) 3 (dppm) 2 ]. Crossover experiments suggest that acetone arises primarily from an intramolecular process. We propose that migratory insertion of a CO and a methyl group occurs on Ir; presumably reductive elimination also occurs from this metal. Compound 2 reacts with H 2 at −78 °C to yield [RhIrH(CH 3 ) 2 (μ-H)(μ-CO)(dppm) 2 ] ( 6 ), in which one methyl group is bound to Rh while the other, together with a hydride ligand, is terminally bound to Ir. This latter species reacts with CO at 0 °C to yield [RhIrH(C(O)CH 3 )(CH 3 )(μ-H)(μ-CO)(dppm) 2 ] ( 7 ), in which migratory insertion involving CO and the Rh-bound methyl group has yielded a Rh-bound acetyl group. At ambient temperature, under an atmosphere of CO, [RhIr(CO) 3 (dppm) 2 ] is formed, together with acetaldehyde and methane. Crossover experiments support a predominantly intramolecular process for acetaldehyde formation but are equivocal on the formation of methane. Compound 2 oxidatively adds CH 3 I or n - C 4 H 9 I, yielding [RhIr(CH 3 ) 2 (R)(μ-I)(μ-CO)(dppm) 2 ] (R = CH 3, n - C 4 H 9 ), in which the added alkyl group in each case is bound to Ir. The n - butyl product reacts with CO to yield [RhIr( n - C 4 H 9 )(CH 3 ) 2 (μ-CO) 2 (dppm) 2 ][I], in which the n - butyl group has migrated to Rh. A similar product, [RhIr(CH 3 ) 3 (μ-CO) 2 (dppm) 2 ][CF 3 SO 3 ], is obtained in the reaction of 2 with methyl triflate in the presence of CO.
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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) | 0.001 | 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) | 0.000 | 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".