Extremely Stable Thorium(IV) Dialkyl Complexes Supported by Rigid Tridentate 4,5-Bis(anilido)xanthene and 2,6-Bis(anilidomethyl)pyridine Ligands
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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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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.044 | 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 it