Synthesis and ligand properties of chelating bis(N-heterocyclic carbene)-stabilized bis(phosphinidenes)
Bibliographic record
Abstract
N-heterocyclic carbene-phosphinidene adducts (NHPs) are an emerging class of ligands with proven binding ability for main group and transition elements. They can be considered as inversely polarized phosphaalkenes with electron-rich P atoms possessing two lone pairs of electrons, which render them interesting platforms for the formation of multi-metallic complexes. We describe herein a modular, high-yielding synthesis of bis(NHP)s, starting from alkylidene-bridged bis(NHC)s ((IMe)}2CnH2n; n = 1,3) and a triphosphirane (cyclo-P3Dip3) (Dip = 2,6-iPr2C6H3) as phosphinidene transfer reagents. The coordination chemistry of [{DipP(IMe)}2CH2], 1, was studied in detail, and the complexes [1∙FeBr2] and [1∙Rh(cod)]Cl were prepared, showing that the ligand has a flexible bite-angle ranging between 86-106°. [1∙Rh(cod)]Cl was converted into the corresponding dicarbonyl complex [1∙Rh(CO)2]Cl, with an average value for the CO stretching frequency of 2029 cm−1, which indicates a strongly donating ligand, when compared to related bis(NHC) rhodium complexes. The binding ability of the remaining two phosphorus lone pairs was demonstrated via addition of AuCl(SMe2), which generated the hetero-trimetallic complex [1∙(AuCl)2∙Rh(cod)]Cl. Moreover, [1∙Rh(cod)]X (X− = Cl, B(3,5-CF3-C6H3)4) were tested in the catalytic hydrogenation of the α,β-unsaturated esters methyl-Z-α-acetamidocinnamate (MAC) and dimethyl itaconate (ItMe2), revealing that the chloride complex was inactive, while the BArF-complex demonstrated moderate activity, lower than that of analogous complexes incorporating classical diphosphines such as DiPAMP. In addition, [1∙Rh(cod)]Cl was shown to be moderately air- and moisture stable, slowly decomposing to the corresponding NHC-stabilized bisdioxophosphorane, which was independently synthesized by treating the free ligand with dry O2.
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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) | 0.001 | 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".