Spectroscopic and DFT Study of Ferraaziridine Complexes Formed in the Transfer Hydrogenation of Acetophenone Catalyzed Using <i>trans</i>-[Fe(CO)(NCMe)(PPh<sub>2</sub>C<sub>6</sub>H<sub>4</sub>CH═NCH<sub>2</sub>−)<sub>2</sub>-κ<sup>4</sup><i>P,N,N,P</i>](BF<sub>4</sub>)<sub>2</sub>
Bibliographic record
Abstract
The reaction of the iron complex trans -[Fe(CO)(MeCN)(PPh 2 C 6 H 4 CH═NCH 2 −) 2 -κ 4 P, N, N, P ](BF 4 ) 2 ( 1 ) with KO i Pr in benzene produced the unusual complex [Fe(CO)(PPh 2 C 6 H 4 CH═NCH 2 CH 2 NHCHC 6 H 4 PPh 2 )-κ 5 P, N, C, N, P ][BF 4 ] ( 2 ), which has been characterized by spectroscopy and by single-crystal X-ray diffraction. The C–N bond length in this complex indicates that it is best viewed as an iron(II) ligand-folded ferraaziridine-κ 2 C, N complex instead of an iron(0) η 2 -iminium complex. Density functional theory (DFT) calculations have been employed on simplified structural models to support a mechanism of formation of this complex via the transfer of a hydride from the alkoxide complex trans- [Fe(CO)(OCHMe 2 )(PH 2 C 6 H 4 CH═NCH 2 −) 2 -κ 4 P, N, N, P ] + ( 4 DFT ) to an imine carbon on the ligand to produce the amide complex trans- [Fe(CO)(OC(CH 3 ) 2 )(PH 2 C 6 H 4 CH═NCH 2 CH 2 NCH 2 C 6 H 4 PH 2 -κ 4 P, N, N, P )] + ( 5 DFT acet ) followed by liberation of acetone to afford 5 DFT . Two energetically similar pathways have been proposed in which deprotonation of the PNNP ligand of 5 DFT by strong base produces the experimentally observed ferraaziridinido complex Fe(CO)(PH 2 C 6 H 4 CH═NCH 2 CH 2 NCHC 6 H 4 PH 2 )-κ 5 P, N, C, N, P ( 3 DFT ) or the square-pyramidal Fe(0) complex Fe(CO)(PH 2 C 6 H 4 CH═NCH 2 −) 2 -κ 4 P, N, N, P ( 7 DFT ). Protonation of 3 DFT by free isopropyl alcohol produces the ferraaziridine complex 2 DFT . Nuclear magnetic resonance and infrared spectroscopy data show that during the transfer hydrogenation of acetophenone catalyzed by 1 in basic isopropyl alcohol, free ligand is observed along with one major iron-containing species identified as 3 . On the basis of our calculations of relative free energies and a CO scale factor, we predict that 2 is easily deprotonated to form the electron-rich iron complex 3 and the square-pyramidal Fe(0) complex 7, which are responsible for the two observed CO stretches below 1900 cm –1 in catalytic mixtures. Mass balance studies indicate that the catalytically active species is not observable by NMR. Although 2 and 3 are poor transfer hydrogenation catalysts, we present experimental and theoretical evidence that ligand folding/distortion is feasible.
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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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".