α-Agostic Interactions in Cp*W(NO)(CH<sub>2</sub>CMe<sub>3</sub>)<sub>2</sub> and Related Nitrosyl Complexes
Bibliographic record
Abstract
The solid-state molecular structure of Cp*W(NO)(CH 2 CMe 3 ) 2 ( 1 ) has been shown to contain one “strongly agostic” and one “weakly agostic” methylene hydrogen atom by a neutron diffraction analysis at 120 K and by an X-ray diffraction analysis at −100 °C. The X-ray diffraction analysis of Cp*W(NO)(CH 2 SiMe 3 ) 2 ( 2 ) at −20 °C reveals that its solid-state molecular structure possesses a crystallographically imposed mirror plane. Consequently, only the average existence of a relatively strong C−H···M interaction for each hydrocarbyl ligand in 2 in the solid state can be established. The 1 H and gated 13 C{ 1 H} NMR spectra of representative Cp‘M(NO)(R)(R‘) (M = Mo, W; R = hydrocarbyl, R‘ = hydrocarbyl, halide, amide) complexes exhibit spectral parameters for the α-H and α-C atoms (i.e., δ H, δ C, Δδ H, Δ J HC, and J HW ) that provide evidence for the presence of α-agostic interactions in the molecular structures of these complexes in solution. The picture that has emerged from these investigations is that these complexes do adopt an α-agostic structure both in solution and in the solid state when secondary interactions such as π-electron donation are weak (as in Cp*W(NO)(CH 2 CMe 3 )Cl), competitive (as in Cp*W(NO)(CH 2 CMe 3 )(CH 2 Ph)), or not possible (as in Cp*W(NO)(hydrocarbyl) 2 complexes generally). The bis(hydrocarbyl) complexes are probably stereochemically nonrigid in solution, as they appear to interconvert between the two limiting structures having one strongly agostic and one weakly agostic hydrocarbyl ligand. The neopentyl ligand forms α-agostic linkages with the metal centers in all neopentyl complexes studied, and these agostic interactions appear to be independent of the nature of the metal or the ancillary cyclopentadienyl ligand. Interestingly, the presence of these ground-state agostic interactions does not correlate with the tendency of the various compounds to undergo intramolecular α-H abstraction reactions and form reactive alkylidene complexes.
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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) | 0.001 | 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".