@article {382,
	title = {Combined solid state NMR and X-ray diffraction investigation of the local structure of the five-coordinate silicon in fluoride-containing as-synthesized STF zeolite},
	journal = {Journal of the American Chemical Society},
	volume = {124},
	number = {26},
	year = {2002},
	note = {ISI Document Delivery No.: 567YYTimes Cited: 41Cited Reference Count: 48},
	month = {Jul},
	pages = {7770-7778},
	type = {Article},
	abstract = {The local structure of the [SiO4/2F](-) unit in fluoride-containing as-synthesized STF zeolite has been experimentally determined by a combination of solid-state NMR and microcrystal X-ray diffraction to be very close to trigonal bipyramidal. Because the fluoride ions are disordered over two sites, the resulting local structure of the [SiO4/2F](-) unit from a conventional XRD refinement is an average between tetrahedral SiO4/2 and five-coordinate [SiO4/2F](-), giving an apparent F-Si distance longer than expected. The correct F-Si distance was determined by slow spinning MAS and fast spinning F-19/Si-29 CP and REDOR solid-state NMR experiments and found to be between 1.72 and 1.79 Angstrom. In light of this, the X-ray structure was re-refined, including the disorder at Si3. The resulting local structure of the [SiO4/2F]- unit was very close to trigonal bipyramidal with a F-Si distance of 1.744 (6) Angstrom, in agreement with the NMR results and the prediction of Density Functional Theory calculations. In addition, further evidence for the existence of a covalent F-Si bond is provided by a F-19{\textendash}>Si-29 refocused INEPT experiment. The resonance for the five-coordinate species at -147.5 ppm in the Si-29 Spectrum is a doublet due to the F-19/Si-29 J-coupling of 165 Hz. The peaks in this doublet have remarkably different effective chemical shift anisotropies due to the interplay of the CSA, dipolar coupling, and J-coupling tensors. The distortions from tetrahedral geometry of the neighboring silicon atoms to the five-coordinate Si3 atom are manifested in increased delta(aniso) values. This information, along with F-Si distances measured by F-19{\textendash}>Si-29 CP experiments, makes it possible to assign half of the Si-29 resonances to unique tetrahedral sites. As well as determining the local geometry of the [SiO4/2F](-) unit, the work presented here demonstrates the complementarity of the solid-state NMR and X-ray diffraction techniques and the advantages of using them together.},
	keywords = {5-COORDINATE SILICON, C-13 NMR, CONTAINING OCTADECASIL, CROSS-POLARIZATION, DISTANCE DETERMINATIONS, LOCATION, MOLECULAR-SIEVES, P-31 NMR, POLARIZATION TRANSFER, PROTON-ENHANCED NMR},
	isbn = {0002-7863},
	url = {<Go to ISI>://000176516400032},
	author = {Fyfe, C. A. and Brouwer, D. H. and Lewis, A. R. and Villaescusa, L. A. and Morris, R. E.}
}
@article {3338,
	title = {INEPT EXPERIMENTS IN SOLID-STATE NMR},
	journal = {Journal of the American Chemical Society},
	volume = {117},
	number = {41},
	year = {1995},
	note = {ISI Document Delivery No.: TB353Times Cited: 38Cited Reference Count: 16},
	month = {Oct},
	pages = {10397-10398},
	type = {Note},
	keywords = {DOUBLE-RESONANCE NMR, ENHANCEMENT, HELICAL PEPTIDE, INTERATOMIC DISTANCE, NUCLEI, POLARIZATION TRANSFER, QUADRUPOLAR, REDOR, SIGNALS, VPI-5},
	isbn = {0002-7863},
	url = {<Go to ISI>://A1995TB35300031},
	author = {Fyfe, C. A. and Wongmoon, K. C. and Huang, Y. and Grondey, H.}
}
