Electronic Effects in PCP-Pincer Ru(II)-Based Hydrogen Transfer Catalysis
Bibliographic record
Abstract
The synthesis and characterization of novel cyclometalated ruthenium(II) complexes [RuCl(PCP OMe )(PPh 3 )] and [RuCl(PCP CF3 )(PPh 3 )] containing monoanionic, tridentate coordinating PCP-pincer ligands [C 6 H 3 {CH 2 P( p -MeOC 6 H 4 ) 2 } 2 -2,6] - (PCP OMe ) and [C 6 H 3 {CH 2 P( p -CF 3 C 6 H 4 ) 2 } 2 -2,6] - (PCP CF3 ) are reported. These compounds have been tested as catalyst precursors in the hydrogen transfer reaction of cyclohexanone to cyclohexanol in 2-propanol using NaOH as a base. The initial rate of the hydrogen transfer reaction appeared to depend on the electronic character of the Ar 2 P− groups of the PCP-pincer ligand. Among the catalyst precursors studied, the complex [RuCl(PCP CF3 )(PPh 3 )] was found to exhibit the highest activity and the initial TOF exceeded that observed for the Ph 2 P analogue [RuCl(PCP Ph )(PPh 3 )]. Most importantly, catalysis performed with [RuCl(PCP CF3 )(PPh 3 )] does not require pretreatment of the precursor in the absence of substrate. Conversely, a different catalytic profile and a low activity were observed when either the electron-poor [RuCl{C 6 H 3 (CH 2 P(C 6 F 5 ) 2 ) 2 -2,6}(PPh 3 )] ([RuCl(PCP F20 )(PPh 3 )]) complex or its triflate analogue was used as catalyst precursors. NMR studies and ESI-MS measurements provided information concerning the catalytically active species formed during the pretreatment of the precursor complexes. The results indicate that during the pretreatment period a monoanionic, monohydride ruthenium(II) species, Na[Ru(H)(PCP i Pr )(O i Pr)(PPh 3 )], is selectively formed. The latter hydride complex was also obtained via an independent synthetic route. On the basis of both the present results and those previously reported in literature, a mechanism is proposed.
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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 | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| 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; 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".