Reaction of the Cyclic Thionylphosphazene NSOCl[NPCl<sub>2</sub>]<sub>2</sub> with Halide Abstraction Agents: An Ambient Temperature Ring-Opening Polymerization (ROP) Route to Poly(thionylphosphazenes)
Bibliographic record
Abstract
The thionylphosphazene cation [NSO(NPCl 2 ) 2 ] + is a proposed intermediate in the thermal ring-opening polymerization of the cyclic thionylphosphazene NSOCl(NPCl 2 ) 2 ( 1 ) at 165 °C. The attempted generation of [NSO(NPCl 2 ) 2 ] + via halide abstraction from 1 with a variety of Lewis acids has been studied and the possible intermediacy of this species in the subsequent reactions is suggested by the products isolated. The thermal reaction of 1 with 2 equivalents of AlCl 3 at 80 °C in 1,2-dichloroethane led to the quantitative formation of NSO(CH 2 CHCl 2 )(NPCl 2 ) 2; reaction of 1 with Ag[BF 4 ] at 25 °C afforded the sulfur(VI)-fluorinated species NSOF(NPCl 2 ) 2 and the treatment of 1 with Ag[OSO 2 CF 3 ] resulted in the quantitative formation of NSO(OSO 2 CF 3 )(NPCl 2 ) 2; the latter species was found to cleave diethyl ether and generate NSO(OCH 2 CH 3 )(NPCl 2 ) 2 . Ambient temperature reaction of 1 with GaCl 3, AlCl 3 or SbCl 5 (10:1), produced the high molecular weight poly(thionylphosphazene) [NSOCl(NPCl 2 ) 2 ] n and, in addition 12-, 18-, 24- and higher-membered macrocycles. Studies showed GaCl 3 as the most effective ROP initiator, and AlCl 3 the least. Subsequent reaction of [NSOCl(NPCl 2 ) 2 ] n with n -BuNH 2 yielded the hydrolytically stable poly(aminothionylphosphazene) [NSO(NHBu){NP(NHBu) 2 } 2 ] n, which possessed molecular weights in the range, M n = 25 000−60 000; PDI = 1.26−2.88. The polymerization reaction studied represents the first example of the ambient temperature ROP of any phosphazene or heterophosphazene ring induced by the deliberate addition of an initiator. Interestingly, the concentration of monomer 1 in solution was found to have a dramatic influence on the extent of reaction and the product distribution. Concentrated solutions of 1 and GaCl 3 (10:1) afforded only [NSOCl(NPCl 2 ) 2 ] n and larger macrocycles, whereas more dilute solutions afforded [NSOCl(NPCl 2 ) 2 ] n together with smaller macrocyclic products with lower conversions. Remarkably, dilute solutions of 1 were found to be unreactive toward GaCl 3 . This existence of a critical equilibrium concentration (∼0.15 M) below which the monomer does not polymerize has only rarely been observed for inorganic systems and is indicative of a polymerization with a small Δ H value which implies that heterocycle 1 is not very strained.
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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".