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

被引:78
作者
Fyfe, CA
Brouwer, DH
Lewis, AR
Villaescusa, LA
Morris, RE
机构
[1] Univ British Columbia, Dept Chem, Vancouver, BC V6T 1Z1, Canada
[2] Univ St Andrews, Sch Chem, St Andrews KY16 9ST, Fife, Scotland
关键词
D O I
10.1021/ja012558s
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
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-->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-->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.
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页码:7770 / 7778
页数:9
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[1]  
[Anonymous], ACS S SER
[2]   Synthesis and characterisation of a linear [Cu(pyr)2]2+ complex in siliceous ferrierite [J].
Attfield, MP ;
Weigel, SJ ;
Taulelle, F ;
Cheetham, AK .
JOURNAL OF MATERIALS CHEMISTRY, 2000, 10 (09) :2109-2113
[3]   True structure of trigonal bipyramidal SiO4F- species in siliceous zeolites [J].
Attfield, MP ;
Catlow, CRA ;
Sokol, AA .
CHEMISTRY OF MATERIALS, 2001, 13 (12) :4708-4713
[4]   Location of fluoride counterion in as-synthesized silicalite-1 by single crystal X-ray diffraction [J].
Aubert, E ;
Porcher, F ;
Souhassou, M ;
Petrícek, V ;
Lecomte, C .
JOURNAL OF PHYSICAL CHEMISTRY B, 2002, 106 (05) :1110-1117
[5]   THE EFFECTS OF INTERPLAY OF SHIELDING, DIPOLAR COUPLING, AND INDIRECT COUPLING TENSORS IN THE SN-119 NMR-SPECTRA OF SOLID TRIORGANYL TIN FLUORIDES [J].
BAI, HP ;
HARRIS, RK .
JOURNAL OF MAGNETIC RESONANCE, 1992, 96 (01) :24-30
[6]   SIMPSON: A general simulation program for solid-state NMR spectroscopy [J].
Bak, M ;
Rasmussen, JT ;
Nielsen, NC .
JOURNAL OF MAGNETIC RESONANCE, 2000, 147 (02) :296-330
[7]   Synthesis and structure of as-prepared ITQ-4, a large pore pure silica zeolite: The role and location of fluoride anions and organic cations [J].
Barrett, PA ;
Camblor, MA ;
Corma, A ;
Jones, RH ;
Villaescusa, LA .
JOURNAL OF PHYSICAL CHEMISTRY B, 1998, 102 (21) :4147-4155
[8]   19F/29Si distance determination in fluoride-containing octadecasil by Hartmann-Hahn cross-polarization under fast magic-angle spinning [J].
Bertani, P ;
Raya, J ;
Reinheimer, P ;
Gougeon, R ;
Delmotte, L ;
Hirschinger, J .
SOLID STATE NUCLEAR MAGNETIC RESONANCE, 1999, 13 (04) :219-229
[9]   Imposition of polarity on a centrosymmetric zeolite host: The effect of fluoride ions on template ordering in zeolite IFR [J].
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Villaescusa, LA ;
Teat, SJ ;
Camblor, MA ;
Wright, PA ;
Lightfoot, P ;
Morris, RE .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2000, 122 (29) :7128-7129
[10]   Synthesis of all-silica and high-silica molecular sieves in fluoride media [J].
Camblor, MA ;
Villaescusa, LA ;
Díaz-Cabañas, MJ .
TOPICS IN CATALYSIS, 1999, 9 (1-2) :59-76