Reactivity of Ruthenium Phosphido Species Generated through the Deprotonation of a Tripodal Phosphine Ligand and Implications for Hydrophosphination
Bibliographic record
Abstract
The fragmentation of the 1,1,2-tris(diphenylphosphino)ethane ligand in [RuCp*((Ph2P)2CHCH2PPh2)][PF6] (1) was explored through treatment with base under aprotic conditions. The neutral phosphido complex RuCp*(PPh2CH═CHPPh2)(PPh2) (2) with a (Z)-1,2-bis(diphenylphosphino)ethene (dppen) ligand was generated through a base-facilitated dehydrophosphination reaction. Installation of a bis(p-tolyl)phosphido ligand was attempted by combining bis(p-tolyl)phosphine with RuCp*(dppen)Cl in the presence of KOtBu, but surprisingly, the unsymmetrical diphenylphosphido compound RuCp*(Ph2PCHCHP(p-tol)2)(PPh2) (5) was generated instead. The ligand rearrangement reaction was driven by the greater electron density on the bis(p-tolyl)phosphido moiety. Density functional theory calculations showed that fragmentation to the 1,2-disubstituted ligand was thermodynamically favored over the 1,1-disubstituted ligand and that intramolecular phosphido exchange was kinetically accessible at room temperature. The greater basicity of the bis(p-tolyl)phosphido ligand was experimentally verified by the measured pKaTHF of 28 for the acid/base pair [RuCp*(Ph2P(o-C6H4)PPh2)(P(p-tolyl)2H)]+/RuCp*(Ph2P(o-C6H4)PPh2)(P(p-tolyl)2) versus 25 for the acid/base pair [RuCp*(Ph2P(o-C6H4)PPh2)(PPh2H)]+/RuCp*(Ph2P(o-C6H4)PPh2)(PPh2) (7). For comparison, the approximate pKaTHF values for free P(p-tolyl)2H/[K(crypt)]P(p-tolyl)2 and free PPh2H/[K(crypt)]PPh2 are 43 and 38, respectively. This is the first quantitative measurement of the large effect that coordination to a metal center, in this case ruthenium(II), has on the acidity of secondary phosphines. This is useful information for designing and understanding hydrophosphination catalysts. Complexes 2 and 7 are catalysts for the addition of PPh2H to acrylonitrile, but they deactivate fairly rapidly. The pKaTHF measurements are consistent with a catalytic cycle involving a Michael addition step. Complex 2 in solution underwent a slow, unprecedented rearrangement of P–C, C–C, and C–H bonds to give crystalline Ru(C5(CH3)4(CH2C6H5))(Ph2PCH2CH2PPh(o-C6H4)PPh) (9) in high yields, demonstrating the unpredictable reactivity of phosphido ligands.
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How this classification was reachedexpand
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".