<i>Trans</i> Ligand Determines the Stability of Paramagnetic Manganese(II) Hydrides of the Type <i>trans</i>-[MnH(L)(dmpe)<sub>2</sub>]<sup>+</sup> Where L is PMe<sub>3</sub>, C<sub>2</sub>H<sub>4</sub>, or CO
Bibliographic record
Abstract
Paramagnetic metal hydride (PMH) complexes play important roles in catalytic applications and bioinorganic chemistry. 3d PMH chemistry has largely focused on Ti, Mn, Fe, and Co. Various Mn II PMHs have been proposed as intermediates in catalysis, but isolated Mn II PMHs are limited to dimeric high-spin Mn II structures with bridging hydrides. In this paper, a series of the first low-spin monomeric Mn II PMH complexes are generated by chemical oxidation of their Mn I analogues. This series is of the type trans -[MnH(L)(dmpe) 2 ] +/0 where the trans ligand L is PMe 3, C 2 H 4, or CO [dmpe is 1,2-bis(dimethylphosphino)ethane], and the thermal stability of the Mn II hydride complexes was found to be strongly dependent on the identity of the trans ligand. When L is PMe 3, the complex is the first example of an isolated monomeric Mn II hydride complex. In contrast, when L is C 2 H 4 or CO, the complexes are only stable at low temperatures; upon warming to room temperature, the former decomposed to afford [Mn(dmpe) 3 ] +, accompanied by ethane and ethylene, whereas the latter eliminated H 2, generating [Mn(MeCN)(CO)(dmpe) 2 ] + or a mixture of products including [Mn(κ 1 -PF 6 )(CO)(dmpe) 2 ], depending on the reaction conditions. All PMHs were characterized by low-temperature electron paramagnetic resonance (EPR) spectroscopy, and stable [MnH(PMe 3 )(dmpe) 2 ] + was further characterized by UV–vis and IR spectroscopy, Superconducting Quantum Interference Device magnetometry, and single-crystal X-ray diffraction. Noteworthy spectral properties are the significant EPR superhyperfine coupling to the hydride (∼85 MHz) and an increase (+33 cm –1 ) in the Mn–H IR stretch upon oxidation. Density functional theory calculations were also employed to gain insights into the acidity and bond strengths of the complexes. Mn II –H bond dissociation free energies are estimated to decrease in the series of complexes from 60 (L = PMe 3 ) to 47 kcal/mol (L = CO).
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.000 | 0.003 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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; both teacher heads agree on what is shown here.
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".