Alkali Metal Amide Salts of a Bulky Nitrogen Tethered Phosphonium Fluorenide Ligand
Bibliographic record
Abstract
The reaction of a previously reported phosphine-imine ligand with 9-bromofluorene afforded a phosphonium bromide (E)-enamine that, upon deprotonation, affords an enamine tethered to a phosphonium fluorenide moiety. Isolation of various crystals of this enamine and subsequent analysis by single-crystal X-ray diffraction showed that both (E)- and (Z)-isomers occur, which is supported by three dynamic isomers in C 6 D 6 . 1 H NMR spectroscopy revealed that the enamine phosphonium fluorenide is the dominant isomer and is also observed within all four solid-state crystal structures of 3 . The solvent-free 3 and 0.5(THF, n-hexane) solvate of 3 occur as the (Z)-enamine, while co-crystallization of either diethyl ether or 3 molecules of THF resulted in the (E)-enamine of 3 . The ability for compound 3 to participate in two types of hydrogen bonds between either the methyne or amine protons with THF was observed from the 0.5(THF, n-hexane) and 3(THF) solvates, respectively. Subsequent deprotonation of the secondary amine with lithium-, sodium-, and potassium-containing bases yielded metal amides, forming mostly monomeric structures. Each alkali metal is chelated by one ligand with a coordinating solvent molecule (Et 2 O or THF), with the only exception being a potassium complex that lacked a coordinating solvent. This potassium complex has this donor vacancy filled by an intermolecular interaction with the backside of an adjacent 6-membered fluorenide ring, forming a polymer with n-hexane within the channels. This crystalline form readily de-solvates upon crushing and prolonged drying in vacuo. The single crystal X-ray structure of these complexes as various solvates with diethyl ether (Li, K), THF (Li, Na), and n-hexane (K) revealed the highly dynamic donor properties of the phosphonium fluorenide undergoing a wide range of η 2–6 interactions with the alkali metals.
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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".