Density Functional Study of the Oxidative Addition Step in the Carbonylation of Methanol Catalyzed by [M(CO)<sub>2</sub>I<sub>2</sub>]<sup>-</sup>(M = Rh, Ir)
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Bibliographic record
Abstract
Quantum mechanical calculations based on density functional theory (DFT) have been carried out on the oxidative addition process [M(CO) 2 I 2 ] - + CH 3 I → [M(CO) 2 I 3 (CH 3 )] - (M = Rh, Ir), which represents an elementary step in methanol carbonylation. The calculated free energies of activation (Δ G ⧧ ) in methanol are 19.3 (Ir) and 26.9 kcal mol - 1 (Rh), respectively, in good agreement with the experimental estimates at 20.9 kcal mol - 1 (Ir) in dichloromethane and 22.9 kcal mol - 1 (Rh) in methanol, respectively. The higher barrier for M = Rh is attributed to a relativistic stabilization of the Ir−CH 3 bond. A thermodynamic calculation was carried out on the formation of the intermediate [M(CO)L 2 ICH 3 ] ( n - 1) - in the general oxidative addition reaction [M(CO)L 2 I] n - + CH 3 I → [M(CO)L 2 ICH 3 ] ( n - 1) - + I - ( n = 0 or 1) (where L 2 = (CO)I -, (CO) 2, or (CO)(MeOH) for M = Ir and L 2 = (CO)I -, trans -(PEt 3 ) 2, Ph 2 PCH 2 CH 2 PPh 2, Ph 2 PCH 2 P(S)Ph 2, or S,P -SC 2 B 10 H 10 PPh 2 - for M = Rh). The thermodynamic energy difference between the intermediate [M(CO)L 2 ICH 3 ] ( n - 1) - and the ground state follows the order S,P -SC 2 B 10 H 10 PPh 2 - < trans -(PEt 3 ) 2 < Ph 2 PCH 2 P(S)Ph 2 < Ph 2 PCH 2 CH 2 PPh 2 < (CO)I - < (CO) 2 in solution with respect to the ligand L 2 . This order is to a first approximation determined by the ability of L to stabilize the M−CH 3 bond being formed and the ability of the solvent to stabilize the intermediate [M(CO)L 2 ICH 3 ] ( n - 1) - relative to ground state. This order agrees well with the experimental kinetic trend.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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