Highly Active Cationic Rhodium(I) Precatalysts for the Ambient Temperature Ring-Opening Polymerization of [1]Silaferrocenophanes and Tetramethyldisilacyclobutane
Bibliographic record
Abstract
The cationic rhodium(I) complexes [Rh(1,5-cod) 2 ]A (A = OTf, PF 6, 1,5-cod = 1,5-cyclooctadiene) have been shown to exhibit high catalytic activity for the transition metal-mediated ring-opening polymerization (ROP) of silicon-bridged [1]ferrocenophanes (e.g., fcSiMe 2 ( 1a ), fc = Fe(η 5 -C 5 H 4 ) 2 ), to quantitatively afford high molecular weight ( M n > 10 5 ) polyferrocenylsilanes (e.g., [fcSiMe 2 ] n ( 2a )). However, prolonged exposure of the resulting polyferrocene solution to the catalyst resulted in a dramatic molecular weight decline. Transition metal-catalyzed ROP of tetramethyldisilacyclobutane ( 6 ) and copolymerization of this species with 1a also proved readily feasible with [Rh(1,5-cod) 2 ]OTf forming high molecular weight polycarbosilane homopolymer ( 7 ) ( M n = 4.20 × 10 5 to 1.08 × 10 6, PDI = 1.39−2.08) and poly(carbosilane- r -ferrocenylsilane) ( 8 ) copolymer ( M n = 4.63 × 10 5, PDI = 1.86), respectively. While [Rh(1,5-cod)(dmpe)]PF 6 (dmpe = bis(dimethylphosphinoethane)) proved less active as a ROP catalyst, this species represents the first phosphine-ligated catalyst for the ROP of 1a, and moreover, in this case no subsequent depolymerization of the resulting poly(ferrocenyldimethylsilane) ( 2a ) was detected. The cleavage of the polyferrocene backbone in the presence of [Rh(1,5-cod) 2 ]OTf was modeled through the catalytic reaction of Fc 2 SiMe 2 (Fc = Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 )) with the rhodium complex (9 mol %), which resulted in Cp−Si bond cleavage affording ferrocene as the sole, isolable product. The presence of 1,5-cod inhibited the catalytic activity of both [Rh(1,5-cod) 2 ]OTf and [Rh(1,5-cod)(dmpe)]PF 6, suggesting that elimination of a 1,5-cod ligand is necessary to generate the true active catalytic species. The addition of dmpe effectively arrested the catalytic activity with [Rh(1,5-cod)(dmpe)]PF 6; this is presumably a result of the displacement of the 1,5-cod ligand by dmpe, which would generate catalytically inactive [Rh(dmpe) 2 ]PF 6 .
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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 | 0.001 |
| 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) | 0.005 | 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".