Destiny of Transient Phosphenium Ions Generated from the Addition of Electrophiles to Phosphaalkenes: Intramolecular C−H Activation, Donor−Acceptor Formation, and Linear Oligomerization
Bibliographic record
Abstract
The reaction of the phosphaalkenes MesP CPh 2 (Mes = 2,4,6-Me 3 C 6 H 2 ) and Mes*P CH 2 (Mes* = 2,4,6- t Bu 3 C 6 H 2 ) with Lewis (AlCl 3, GaCl 3, InCl 3 ) and protic (HOTf) acids has been examined to evaluate the feasibility of cationic polymerization for P C bonds. Addition of GaCl 3 to Mes*P CH 2 generates the adduct Mes*(Cl 3 Ga)P CH 2, which can be detected spectroscopically at 193 K. At higher temperatures, GaCl 3 migrates from phosphorus to carbon to afford the fleeting phosphenium zwitterion Mes*PCH 2 GaCl 3 . This undetected transient species immediately oxidatively adds to a C−H bond of an o - t Bu group in the P -Mes* substituent, resulting in a GaCl 3 -coordinated ylide that has been characterized crystallographically. The analogous reaction of GaCl 3 with MesP CPh 2 gives stable Mes(Cl 3 Ga)P CPh 2, for which a crystal structure determination has been conducted. Significantly, treating a highly concentrated solution of Mes*P CH 2 with substoichiometric quantities of GaCl 3 leads to linear dimerization following a cationic chain growth mechanism; however, the oligomerization is terminated by intramolecular C−H activation. The novel coordinated linear dimer (C−H activated Mes*)PCH 2 PH(Mes*)CH 2 GaCl 3 has been characterized crystallographically. Interestingly, mechanistic studies reveal that the diphosphiranium ring derived from the reaction of Mes*PCH 2 GaCl 3 with Mes*P CH 2 is an intermediate in this transformation. The reaction of phosphaalkenes with phosphenium species appears to be a general method to prepare diphosphiranium ions. In one case, NMR spectroscopic data suggests that treating MesP CPh 2 with HOTf gives both the diphosphiranium species and the adduct Ph 2 C (Mes)P→P(Mes)(CHPh 2 )]OTf. Remarkably, treating concentrated Mes*P CH 2 solutions with HOTf results in oligomers of up to six repeat units, as determined by ESI mass spectrometry. These results suggest that it may be possible to initiate the polymerization of P C bonds using cationic initiators and that the propagating species will be a cationic phosphenium moiety.
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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) | 0.002 | 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".