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Functionalised polyhedral oligomeric silsesquioxane with encapsulated fluoride – first observation of fluxional Si⋯F interactions in POSS
Dalton Transactions ( IF 4 ) Pub Date : 2020-11-13 , DOI: 10.1039/d0dt03057k
Mathilde Laird 1, 2, 3, 4, 5 , Cédric Totée 1, 2, 3, 4, 5 , Philippe Gaveau 1, 2, 3, 4, 5 , Gilles Silly 1, 2, 3, 4, 5 , Arie Van der Lee 2, 3, 4, 6, 7 , Carole Carcel 1, 2, 3, 4, 5 , Masafumi Unno 8, 9, 10, 11 , John R. Bartlett 12, 13, 14 , Michel Wong Chi Man 1, 2, 3, 4, 5
Affiliation  

The synthesis of a styryl functionalised POSS incorporating an encapsulated fluoride ion within a (SiO1.5)8 cage (T8-F) is reported. It was characterised by single crystal XRD, MALDI-MS, FTIR, solution (29Si, 19F, 13C, 1H) and solid state (29Si, 19F) NMR. In the absence of 1H decoupling, the 29Si solution NMR spectrum exhibited a triplet of doublets. In contrast, 1H, 19F and 1H/19F double-decoupling resulted in two, three and one signal, respectively, being consistent with a single Si site whose 29Si NMR signal is modulated by both the proximal aromatic-ring protons and fluoride. The associated Si⋯F coupling constant (2.5 Hz) is substantially lower than expected for a covalent Si–F bond and arises from a fluxional Si⋯F covalent effect in which the F interacts equivalently with all eight Si atoms. Additional variable temperature NMR studies demonstrated a threshold at −5 °C below which no Si⋯F interactions are observed, and above which an increasing Si⋯F covalent character occurs.

中文翻译:

功能化的多面体低聚倍半硅氧烷与氟化物包封– POSS中通量Si⋯F相互作用的首次观察

报道了在(SiO 1.58笼(T 8 -F)内掺入封装的氟离子的苯乙烯基官能化的POSS的合成。其特征在于单晶XRD,MALDI-MS,FTIR,溶液(29 Si,19 F,13 C,1 H)和固态(29 Si,19 F)NMR。在没有1 H解耦的情况下,29 Si溶液的NMR光谱显示出三重峰。相反,1 H,19 F和1 H / 19F双重解耦分别产生两个,三个和一个信号,与单个Si位点一致,该位点的29 Si NMR信号受近端芳环质子和氟化物的调节。相关联的Si⋯˚F偶合常数(2.5赫兹)基本上低于预期为共价的Si-F键和从fluxional硅⋯˚F共价效应产生,其中在F -等效所有八个Si原子相互作用。额外的可变温度NMR研究表明,在-5°C下存在一个阈值,低于该阈值未观察到Si⋯F相互作用,而在该阈值之上出现了递增的Si⋯F共价特征。
更新日期:2020-11-21
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