Ring-Opening Polymerization Behavior of <i>ansa</i>- and Spirocyclic <i>ansa</i>-Zirconocene Complexes
Bibliographic record
Abstract
Attempts to develop a ring-opening polymerization (ROP) approach to polymeric zirconocene complexes are reported. A new silicon-bridged [1][1]zirconocenophane, (SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 Zr(NEt 2 ) 2 ( 3a ), was synthesized by reaction of Zr(NEt 2 ) 4 with (C 5 H 4 ) 2 (SiMe 2 ) 2 ( 4 ). Single-crystal X-ray diffraction revealed a highly tilted structure with an angle of 73.1(4)°, a significant increase over the untethered compound ( η 5 -MeC 5 H 4 ) 2 ZrCl 2 ( 2 ), which possesses a tilt angle of 54.2°. This and the related compounds (SiMe 2 )( η 5 -C 5 H 4 ) 2 MCl 2 ( 1a, M = Ti; 1b, M = Zr) and (SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 ZrCl 2 ( 3b ) were tested for transition-metal catalyzed ROP behavior in the presence of Pt(0) catalysts but were found to be inactive. The novel spirocyclic silacyclobutane-bridged monomer (CH 2 ) 3 Si( η 5 -C 5 H 4 ) 2 ZrCl 2 ( 7b ) was prepared via a “fly trap” amine elimination reaction between cyclotrimethylenedicyclopentadienylsilane ( 8 ) and Zr(NMe 2 ) 4; this initially yielded (CH 2 ) 3 Si( η 5 -C 5 H 4 ) 2 Zr(NMe 2 ) 2 ( 7a ), which was converted to 7b by reaction with a slight excess of Me 3 SiCl. 7a and 7b were characterized by 29 Si, 13 C, and 1 H NMR spectroscopy and mass spectrometry as well as single-crystal X-ray diffraction. Both showed moderate tilt angles (61.7(2)° and 59.69(7)°, respectively) as well as highly strained silacyclobutane rings with C−Si−C bond angles of 79.7(2)° and 80.64(10)°, respectively. Transition-metal-catalyzed ROP of 7b led to the formation of the polycarbosilane [(CH 2 ) 3 Si( η 5 -C 5 H 4 ) 2 ZrCl 2 ] n ( 10 ). Both the soluble and insoluble fractions of 10 were characterized by CP-MAS 29 Si and 13 C NMR, and the soluble, oligomeric fraction was further characterized by solution 29 Si, 13 C, and 1 H NMR. Complexes 7a, 7b, and polyzirconocene 10 were found to exhibit moderate activity as ethylene polymerization catalysts.
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How this classification was reachedexpand
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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.023 | 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 teacher head, 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".