Issue 1, 2021

Functionalised polyhedral oligomeric silsesquioxane with encapsulated fluoride – first observation of fluxional Si⋯F interactions in POSS

Abstract

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.

Graphical abstract: Functionalised polyhedral oligomeric silsesquioxane with encapsulated fluoride – first observation of fluxional Si⋯F interactions in POSS

Supplementary files

Article information

Article type
Paper
Submitted
01 Sep 2020
Accepted
11 Nov 2020
First published
13 Nov 2020

Dalton Trans., 2021,50, 81-89

Functionalised polyhedral oligomeric silsesquioxane with encapsulated fluoride – first observation of fluxional Si⋯F interactions in POSS

M. Laird, C. Totée, P. Gaveau, G. Silly, A. Van der Lee, C. Carcel, M. Unno, J. R. Bartlett and M. Wong Chi Man, Dalton Trans., 2021, 50, 81 DOI: 10.1039/D0DT03057K

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