Substituent exchange reactions of trimeric and tetrameric aryloxycyclophosphazenes with sodium 2,2,2-trifluoroethoxide

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 41; no. 7; pp. 21 - 219
• Main Authors: Liu, Xiao, Breon, Jonathan P, Chen, Chen, Allcock, Harry R
• Format: Journal Article
• Language: English
• Published: England 21.02.2012
• Subjects: Displacement; Ethers; Exchange; Exchanging; Mass spectrometry; Nucleophiles; Sodium; Trimers
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c1dt11606a

Substituent exchange reactions of sodium 2,2,2-trifluoroethoxide with trimeric and tetrameric aryloxycyclophosphazenes with phenoxy, 4-formylphenoxy, 4-cyanophenoxy and 4-nitrophenoxy side groups were conducted at 66 C in THF and monitored by 31 P NMR and mass spectrometry. These are model reactions for their counterparts with high polymeric linear organophosphazenes. The ease of displacement of OAr in cyclic trimeric and tetrameric molecules by CF 3 CH 2 O increased significantly with the presence of electron-withdrawing substituents in the polyphosphazene in the order, phenoxy < 4-formylphenoxy < 4-cyanophenoxy 4-nitrophenoxy. Fully substituted 2,2,2-trifluoroethoxyphosphazene trimer and tetramer were formed by side group exchange, but these reactions were followed by an attack by the nucleophile on the -carbon of the 2,2,2-trifluoroethoxy groups linked to phosphorus to give a species in which one trifluoroethoxy group had been replaced by an ONa unit, and bis(trifluoroethyl) ether was formed as a side product. On the other hand, only partly exchanged species were formed when sodium phenoxide reacted with the trifluoroethoxy phosphazene trimer and tetramer, but again a product with an ONa side group was formed eventually together with phenyltrifluoroethyl ether generated via alpha-carbon attack. The relative sensitivity of 2,2,2-trifluoroethoxy and phenoxyphosphazene cyclic trimers and tetramers to the presence of trifluoroethoxide was established. This paper is concerned with the substituent exchange reactions of NaOCH 2 CF 3 with cyclic trimeric and tetrameric aryloxycyclophosphazene derivatives and studies of the subsequent cleavage reaction by an attack by the nucleophile on the -carbon of the trifluoroethoxy groups in the trimer or tetramer.