Phosphoramidate-Assisted Alkyne Activation: Probing the Mechanism of Proton Shuttling in a N,O-Chelated Cp*Ir(III) Complex
Bibliographic record
Abstract
Ligand lability offers a unique opportunity for access to metal–ligand cooperativity (MLC), helping to direct new organometallic and catalytic reactions. In recent years, ligand-assisted C–H bond activation and, more generally, proton migration have been of particular interest. This paper describes a detailed computational study into the mechanism, as well as the region and stereoselectivity, observed in a recently reported transformation where MLC in a 16-electron iridium(III) phosphoramidate complex plays a critical role in directing the activation of terminal alkynes toward the generation of novel five-membered (E)-vinyloxyirida(III)cycles. Five possible pathways for the formation of such products were investigated. Based on our findings, it is proposed that the reaction proceeds via a ligand-assisted proton shuttle (LAPS) mechanism, where the phosphoramidate phosphoryl (P═O) group assists in both alkyne C–H bond activation and C–H bond formation to form a vinylidene intermediate. Next, C–O bond formation occurs via nucleophilic attack at the α-carbon of the vinylidene, giving the observed product. Although C–N (and not C–O) bond formation is thermodynamically favored in this model system, this trend is not observed experimentally, and the computational study suggests that the observed regioisomer is simply the kinetic reaction product. In terms of stereoselectivity, formation of the (E)-irida(III)cycle is explained by its thermodynamic stability, when compared to that of the Z-isomer, and the relatively low barrier to interconversion between them.
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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 | 0.001 | 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) | 0.007 | 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".