Solid-State Chlorine NMR of Group IV Transition Metal Organometallic Complexes
Bibliographic record
Abstract
Static solid-state (35)Cl (I = (3)/(2)) NMR spectra of the organometallic compounds Cp(2)TiCl(2), CpTiCl(3), Cp(2)ZrCl(2), Cp(2)HfCl(2), Cp*(2)ZrCl(2), CpZrCl(3), Cp*ZrCl(3), Cp(2)ZrMeCl, (Cp(2)ZrCl)(2)mu-O, and Cp(2)ZrHCl (Schwartz's reagent) have been acquired at 9.4 T with the quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) sequence in a piecewise manner. Spectra of several samples have also been acquired at 21.1 T. The electric field gradient (EFG) tensor parameters, the quadrupolar coupling constant (C(Q)) and quadrupolar asymmetry parameter (eta(Q)), are readily extracted from analytical simulations of the spectra. The (35)Cl EFG and chemical-shift tensor parameters are demonstrated to be sensitive probes of metallocene structure and allow for differentiation of monomeric and oligomeric structures. First-principles calculations of the (35)Cl EFG parameters successfully reproduce the experimental values and trends. The origin of the observed values of C(Q)((35)Cl) are further examined with natural localized molecular orbital (NLMO) analyses. The combination of experimental and theoretical methods applied to the model compounds are employed to structurally characterize Schwartz's reagent (Cp(2)ZrHCl), for which a crystal structure is unavailable. Aside from a few select examples of single-crystal NMR spectra, this is the first reported application of solid-state (35)Cl NMR spectroscopy to molecules with covalently bound chlorine atoms. It is anticipated that the methodology outlined herein will find application in the structural characterization of a wide variety of chlorine-containing transition-metal and main-group systems.
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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 | 0.001 | 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".