Extremely Stable Thorium(IV) Dialkyl Complexes Supported by Rigid Tridentate 4,5-Bis(anilido)xanthene and 2,6-Bis(anilidomethyl)pyridine Ligands
Bibliographic record
Abstract
A new NON-donor ligand, 4,5-bis(2,6-diisopropylanilino)-2,7-di- tert -butyl-9,9-dimethylxanthene (H 2 [XA 2 ], 1 ), was prepared by palladium-catalyzed coupling of 2,6-diisopropylaniline with the appropriate dibromoxanthene precursor. Stable K 2 (dme) 2 [XA 2 ] ( 2 ) and Na 2 [XA 2 ] ( 3 ) salts were accessible by deprotonation of H 2 [XA 2 ] with KH in dme or NaH in toluene. The thermally unstable lithium salt of McConville's 2,6-bis(2,6-diisopropylanilidomethyl)pyridine ligand (Li 2 [BDPP], 4 ) was isolated by deprotonation with n BuLi or LiCH 2 SiMe 3 in hexanes at low temperature. Reaction of [ThCl 4 (dme) 2 ] with Li 2 [BDPP] or M 2 (dme) n [XA 2 ] resulted in the formation of pentagonal bipyramidal [LThCl 2 (dme)] complexes (L = BDPP, 5; XA 2, 6 ). Subsequent reaction of 5 or 6 with LiCH 2 SiMe 3 gave base- and salt-free dialkyl complexes, [LTh(CH 2 SiMe 3 ) 2 ] (L = BDPP, 7; XA 2, 8 ), which are stable for days in solution at 90 and 70 °C, respectively. Complexes 5, 7, and 8 were also accessible by initial combination of 2 or 4 equiv of LiCH 2 SiMe 3 with [ThCl 4 (dme) 2 ], followed by addition of H 2 L. These reactions likely proceed by alkane elimination, but dialkyl or tetraalkyl thorium intermediates were not identified. The X-ray crystal structure of 8 suggests the presence of α-agostic C−H−Th interactions for both alkyl groups. In solution, 7 and 8 exhibit temperature-dependent 1 J C,H coupling constants for Th CH 2, demonstrating the presence of α-agostic interactions which become increasingly favored at lower temperature. Reaction of 5 with Li 2 [BDPP] at 0 °C or 7 with H 2 [BDPP] at 100 °C resulted in the formation of extremely sterically encumbered [Th(BDPP) 2 ] ( 9 ), which adopts a highly distorted six-coordinate geometry with the four anilido groups arranged in an approximate tetrahedron around thorium. Bis-ligand complexes were not accessible with the XA 2 platform, presumably due to increased ligand rigidity.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".