Influences of N-Heterocyclic Carbene and PMe<sub>3</sub>Ligands on the Tautomerism between Methylene/Hydride and Bridging Methyl Complexes of Rh/Os and Unusual Examples of Ligand Deprotonation by the NHC Group
Bibliographic record
Abstract
The complexes [RhOsL(CO) 3 (dppm) 2 ][CF 3 SO 3 ] (L = IMe 4 (1,3,4,5-tetramethylimidazol-2-ylidene) ( 6 ), PMe 3 ( 8 ); dppm = μ-Ph 2 PCH 2 PPh 2 ) were prepared by substitution of a carbonyl ligand in [RhOs(CO) 4 (dppm) 2 ][CF 3 SO 3 ]. Reaction of 6 with additional IMe 4 resulted in deprotonation of a dppm ligand, yielding [RhOs(IMe 4 )(CO) 3 (μ-κ 1:κ 1 -Ph 2 PCHPPh 2 )(dppm)] ( 7 ). Although reaction of 8 with diazomethane at −78 °C yielded the known methylene-bridged [RhOs(PMe 3 )(CO) 3 (μ-CH 2 )(dppm) 2 ][CF 3 SO 3 ] ( 3 ), compound 6 was unreactive toward diazomethane over a wide temperature range. The methylene-bridged species [RhOs(IMe 4 )(CO) 2 (μ-CH 2 )(dppm) 2 ][CF 3 SO 3 ] ( 9 ) was obtained by reaction of [RhOs(CO) 3 (μ-CH 2 )(dppm) 2 ][CF 3 SO 3 ] with IMe 4, although [RhOs(CO) 3 (μ-CH 2 )(μ-κ 1:η 2 -Ph 2 PCHPPh 2 )(dppm)] ( 10 ) was also obtained by competing dppm deprotonation by IMe 4 . Protonation of [RhOsL(CO) 2 (μ-CH 2 )(dppm) 2 ][CF 3 SO 3 ] (L = IMe 4 ( 9 ), PMe 3 ( 11 )) with triflic acid at −78 °C yielded two isomers in each case. The more abundant isomer, [RhOsL(CO) 2 (μ-CH 3 )(dppm) 2 ][CF 3 SO 3 ] 2, has a bridging agostic methyl group, while the minor isomer has a terminal, Os-bound methyl group. Upon warming, both isomers transformed to species having an Os-bound methyl group and a coordinated triflate ion, subsequently rearranging to the thermodynamic products [RhOsL(CO) 2 (μ-H)(μ-CH 2 )(dppm) 2 ][CF 3 SO 3 ] 2 near ambient temperature. Attempts to prepare an IMe 4 -containing methyl species directly via triflate ion substitution in [RhOs(CH 3 )(OSO 2 CF 3 )(CO) 3 (dppm) 2 ][CF 3 SO 3 ] by IMe 4 instead resulted in deprotonation of the methyl group to give the known product [RhOs(CO) 3 (μ-CH 2 )(dppm) 2 ][CF 3 SO 3 ]. Addition of methyl triflate to 6 gave no reaction, but protonation of 6 with triflic acid at −78 °C yielded the kinetic isomer of [RhOsH(IMe 4 )(CO) 3 (dppm) 2 ][CF 3 SO 3 ] 2, in which the hydride is terminally bound to Os, and warming this product to ambient temperature resulted in rearrangement to the hydride-bridged, thermodynamic isomer.
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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".