Equilibration between a Phosphine−Cobalt Complex and an Analogous Complex Containing an N-Heterocyclic Carbene: The Thermodynamics of a Phosphine−Carbene Exchange Reaction
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Bibliographic record
Abstract
The reaction of CpCo(PPh 3 )Me 2 with the N-heterocyclic carbene 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) does not result in complete substitution of the PPh 3, as expected, but rather in an equilibrium mixture of CpCo(PPh 3 )Me 2, IPr, CpCo(IPr)Me 2, and PPh 3 . Determination of the equilibrium constants for this unusual reaction over the temperature range 30−50 °C shows that Δ H ° = −24.4 ± 1.7 kJ mol - 1, Δ S ° = −65.8 ± 5.5 J mol - 1 K - 1, and thus that it is entropy factors arising from steric crowding in CpCo(IPr)Me 2 that prevent complete substitution. Evidence for steric crowding is found in a comparison with the crystal structures of CpCo(PPh 3 )Me 2, CpCo(IPr)Me 2, and CpCo(IPr)(CO). The smaller, more basic PMe 3 does displace IPr completely from CpCo(IPr)Me 2 .
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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