Bimetallic, Spirocyclic, Methylene-Bridged Carbene Complexes of Rhodium and Palladium Derived by Stepwise Metalations of Lithiated Bis(diphenylphosphoranotrimethylsilylimido)methandiide
Bibliographic record
Abstract
The Li−C−Rh, bimetallic, phosphinimine spirocyclic, bridged carbene complex 1 was readily prepared from dilithiobis(diphenylphosphoranosilylimido)methandiide, [ Li 2 L ] 2, and an equimolar (Rh/Li, 1:1) amount of [Rh(cod)Cl] 2 . Subsequent reaction with a different metal precursor, in the present cases, [Pd(allyl)Cl] 2, yielded the spirocyclic Rh−Pd heterobimetallic 2 or, if a second equivalent of [Rh(cod)Cl] 2 was used, the spirocyclic Rh−Rh homobimetallic 3 was obtained; thus the system presents an effective synthetic route for the preparation of homo- or heterobimetallic complexes. All of the complexes have constrained symmetry, which creates in some cases isomeric and enantiomeric structures. The Li−Rh complex 1 thermally rearranged to the chelated, orthometalated, Rh complex 6, wherein the Rh(I) center is bound to the ipso carbon of a phenyl ring and a methine carbon formed from protonation of the spiro carbon. Remarkably, controlled hydrolysis of 6 reversed the orthometalation and provided an iminophosphorane-methine chelate complex of Rh(I), 7 . Reactions of the cod-substituted complexes 2, 3, and 7 with CO resulted in the replacement of cod substituents to form parallel Rh carbonyl complexes ( 4, 5, and 8 ). The allyl substituents in the system were not affected. The carbonyl complexes 5 and 8 could be made independently from [Rh(CO) 2 Cl] 2 and either the dilithium methandiide or the methine form of the ligand as appropriate. Complexes 2 − 7 have been structurally characterized herein. Complexes 3 and 5 are chiral (because they lack rotation−reflection axes), but the products here are unresolved racemic mixtures according their NMR spectra. The complex 2 and its derivative 4 exist as unequal diastereomeric pairs according to the NMR. Fluxional NMR behavior is observed for 1, wherein the cod appears to partly dissociate and invert, for 2 and 3 where the cod exchange appears to involve a different mechanism being assisted by dissociation of one imine substituent, for 2 and 4 wherein allyl syn−syn, anti−anti exchange occurs between the diastereomers, and for 7 wherein the coordinated and uncoordinated imine groups exchange.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".