Scandium Alkyl and Hydride Complexes Supported by a Pentadentate Diborate Ligand: Reactions with CO2 and N2O
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Bibliographic record
Abstract
Alkyl and hydrido scandium complexes of the dianionic pentatdentate ligand B<sub>2</sub>Pz<sub>4</sub>Py are reported. The key starting material (B<sub>2</sub>Pz<sub>4</sub>Py)ScCl is readily prepared and alkylated with organolithium reagents RLi (R = CH<sub>3</sub>, CH<sub>2</sub>SiMe<sub>3</sub>, CH<sub>2</sub>SiMe<sub>2</sub>Ph, CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub> and CH<sub>2</sub>CHMe<sub>2</sub>) to form alkyl derivatives in 61-93% yields. These compounds are very thermally stable and do not undergo sigma bond metathesis reactions with dihydrogen. The hydrido complex was prepared from (B<sub>2</sub>Pz<sub>4</sub>Py)ScCl and NaHBEt<sub>3</sub> in 80% yield and was found to be more stable by 28 kcal mol<sup>-1</sup> as a dimer, rather than a monomeric hydrido complex. However, the monomer is accessible through dissociation of the dimer at 80˚C. All of the compounds (B<sub>2</sub>Pz<sub>4</sub>Py)ScR react with water to form the bridging oxo dimer (B<sub>2</sub>Pz<sub>4</sub>Py)ScOSc(B<sub>2</sub>Pz<sub>4</sub>Py). The reactivity of the hydrido and methyl complexes towards carbon dioxide was explored; heating to 80˚C results in the formation of k<sup>2</sup> formato and acetate complexes, respectively. The mechanisms were studied via density function theory and distinct transition states for insertion of CO<sub>2</sub> into the Sc-R (R = H, CH<sub>3</sub>) were found, with the insertion into the Sc-CH<sub>3</sub> being more enthalpically difficult (by 18 kcal mol<sup>-1</sup>) than insertion into Sc-H. The slow rate of reaction between [(B<sub>2</sub>Pz<sub>4</sub>Py)ScH]<sub>2</sub> and CO<sub>2</sub> is attributed to the barrier associated with dimer dissociation. In both insertion reactions, the kinetic products are k<sup>1</sup> formato or acetate complexes that are only slightly less stable than the observed k<sup>2</sup> derivatives. The k<sup>1</sup> compounds can therefore be trapped by treating the k<sup>2</sup> isomers with <i>tris</i>-pentafluorophenyl borane.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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 it