One-Electron Oxidations of the Methyldiphenylphosphonium Cyclopentadienylide Complexes M(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>PMePh<sub>2</sub>)(CO)<sub>3</sub> (M = Cr, Mo, W): Formation and Dimerization of the 17-Electron, Metal-Centered Radicals [M(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>PMePh<sub>2</sub>)(CO)<sub>3</sub>]<sup>+</sup>
Bibliographic record
Abstract
Electrochemical oxidations of the group 6 metal complexes M(η 5 -C 5 H 4 PMePh 2 )(CO) 3 (M = Cr ( 1 ), Mo ( 2 ), W ( 3 )) occur via one-electron processes at potentials that are highly positive of the values previously observed for the analogous 18-electron anions [M(η 5 -C 5 H 5 )(CO) 3 ] - . A value of +0.44 V was determined for the electronic effect of the R = [PMePh 2 ] + group compared to R = H in a C 5 H 4 R ligand, making it one of the most strongly electron-withdrawing substituents known. On the basis of the experimentally determined oxidation potentials and observations that the oxidized species were long-lived, bulk oxidations of 1, 2, and 3 by [FeCp 2 ][B(C 6 F 5 ) 4 ] were carried out to give the crystalline, dimeric products [M(η 5 -C 5 H 4 PMePh 2 )(CO) 3 ] 2 [B(C 6 F 5 ) 4 ] 2 (M = Cr ( 1 2 2+ ), Mo ( 2 2 2+ ), and W ( 3 2 2+ )). These were isolated analytically pure and were characterized by IR (solid state and solution) and NMR ( 1 H, 13 C, 19 F, 31 P) spectroscopy, high-resolution mass spectrometry, and crystallographically. The dimers all contain metal−metal bonds that are comparable in length with or longer than the metal−metal bonds in the isoelectronic, neutral η 5 -C 5 H 5 and η 5 -C 5 Me 5 analogues, and the metal−metal bond in 1 2 2+ is the longest nonbridged Cr−Cr bond known. As a result of the apparent weakness of its Cr−Cr bond, 1 2 2+ dissociates significantly in solution to the paramagnetic radical cation 1 +; the 1 H NMR spectrum of this complex in THF at 298 K exhibits characteristic C 5 H 4 resonances at δ 26.08 and 13.62.
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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) | 0.002 | 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 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".