Crystallographic Investigation of Substituted Allyl and Titanacyclobutane Complexes of Bis(2-<i>N</i>,<i>N</i>-dialkylaminoindenyl)titanium. Structure and Reactivity as a Function of the Dialkylamino Substituents
Bibliographic record
Abstract
Substituted allyl complexes of bis(2- N, N -dialkylaminoindenyl)titanium(III) undergo highly regioselective central carbon alkylation upon treatment with organic free radicals, providing a general synthesis of 2,3-disubstituted titanacyclobutane complexes. This reactivity contrasts that of the corresponding bis(pentamethylcyclopentadienyl)titanium(III) series, for which titanacyclobutane formation is observed only in reactions of the unsubstituted allyl complex. Unexpectedly, the radical alkylation is more general for complexes of bis(2- N, N -dimethylaminoindenyl)titanium than complexes of the closely analogous bis(2-piperidinoindenyl)titanium, despite only subtle differences between the two ancillary ligands. In addition, the 2-methyl-3-alkyltitanacyclobutane complexes derived from alkylation of bis(2- N, N -dimethylaminoindenyl)titanium(η 3 -crotyl) are more thermally robust than those derived from the 2-piperidinoindenyl ligand system, resisting decomposition via β-hydride elimination from the α-methyl substituent. To gain insight into the function of the dialkylaminoindenyl ligands and to probe the differences between 2- N, N -dimethylaminoindenyl and 2-piperidinoindenyl complexes, crystal structures of bis(2- N, N -dimethylaminoindenyl)titanium(η 3 -1-phenylallyl) ( 4a ) and bis(2- N, N -dimethylaminoindenyl)titanium(η 3 -crotyl) ( 4b ) have been determined and compared to the crystal structure of bis(2-piperidinoindenyl)titanium(η 3 -1-phenylallyl), 3a . The effects of allyl coordination on the disposition of the dialkylaminoindenyl ligands are revealed by a comparison with the crystal structure of the corresponding chloride complex, bis(2- N, N -dimethylaminoindenyl)titanium(III)chloride·lithium chloride·(THF) 2, a rare Ti(III)halide/lithium halide adduct. Although it is difficult to control for the effects of crystal packing forces, substantial changes in ancillary ligand structure and orientation are observed as a function of the amino substituent and the coordination environment. The difference in titanacyclobutane stability and the response of the dialkylaminoindenyl ligands to the change in oxidation state have been investigated by comparing the crystal structures of two disubstituted titanacyclobutane complexes, 3-isopropyl-2-phenylbis(2-piperidinoindenyl)titanacyclobutane ( 7 ) and 3-isopropyl-2-phenylbis(2- N, N -dimethylaminoindenyl)titanacyclobutane ( 8 ), each prepared by free radical alkylation.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".