Zirconium Alkyl Complexes Supported by Ureate Ligands: Synthesis, Characterization, and Precursors to Metal−Element Multiple Bonds
Bibliographic record
Abstract
A series of bis(ureate) zirconium complexes bearing reactive alkyl ligands have been prepared and fully characterized. A sterically demanding, nontethered ureate ligand was successfully employed in the synthesis of a dibenzyl complex; however synthesis can be complicated by suspected ligand disproportionation and redistribution. In contrast, tethered bis(ureate) ligands, including a chiral, C 2 -symmetric ligand, are reliable supports for sterically accessible, mononuclear dibenzyl and bis(neopentyl) complexes. These coordinatively unsaturated species react with pyridine to form seven-coordinate adducts that exhibit remarkable thermal and photochemical stability. The reactive nature of the dibenzyl derivative can be exploited in the synthesis of imido complexes via protonolysis with 2,6-diisopropylaniline. A monometallic imido, supported by a sterically open ureate ligand, can be prepared in this manner with the use of excess pyridine; however, NMR spectroscopy indicates that this species undergoes dimerization in solution. When the reaction is performed in the absence of pyridine, only the dimeric complex is obtained.
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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".