Measuring the silion fluoride bond distance in zeolites

A common misconception is that X-ray diffraction is the best way to measure bond distances. However, in some cases where disorder is present it can yield incorrect answers. The silicon-fluoride bond distance in fluoride-containing zeolite SFF has been measured using two magic angle spinning NMR techniques. Both techniques, variable contact time cross polarization and spinning side band intensity fitting give shorter Si-F bond distances than X-ray diffraction.