Solid State NMR Interaction Parameters of Oxygens Linking Titanium and Silicon in Crystalline Cyclic Titanodiphenylsiloxanes

A multinuclear solid state NMR study of the sol–gel formation of amorphous Nb2O5–SiO2 materials

“…17 O NMR has been shown for a given metal (i.e. for an M-O bond) to be extremely sensitive to changes in the coordination of the metal [27,28] since this changes the electron hybridisation and density at the oxygen. Also Nb-O-Nb in a purely niobia domain would have a very different electron density to the same bond dispersed in a silica matrix and this should produce a noticeable chemical shift.…”

“…93 Nb is still a relatively little studied nucleus (nuclear spin ðIÞ ¼ 9=2) even though it is 100% naturally abundant. The high spin and relatively high Larmor frequency means that the second-order quadrupolar broadening of the central transition should, for a site of the same distortion, be only $28% broader than the commonly studied quadrupolar nucleus 27 Al. However 93 Nb resonances tend to be much broader than those typically observed for 27 Al.…”

“…The high spin and relatively high Larmor frequency means that the second-order quadrupolar broadening of the central transition should, for a site of the same distortion, be only $28% broader than the commonly studied quadrupolar nucleus 27 Al. However 93 Nb resonances tend to be much broader than those typically observed for 27 Al. For example, the values reported for the 93 Nb quadrupole interactions from a range of niobates (Table 10.6 in Ref.…”

New Opportunities for High-Resolution Solid-State NMR Spectroscopy of Oxide Materials at 21.1- and 18.8-T Fields

“…As early as 1995, 27 Al MAS data collected with "narrow bore" 17.6 T magnets provided enhanced distinction among tetrahedral sites in zeolites [1] and was used to study crystalline B 4 Al 18 O 33 [2]; more recently, this approach at 18.8 T was crucial in resolving the problem of "missing aluminum" in spectra of USY-type zeolites [3,4], in determining the mechanism of solid solution of Al 2 O 3 in 1 to 3 mg samples of perovskite-phase MgSiO 3 synthesized at 26 GPa pressure [5], and in detecting low concentrations (≈ 1%) of AlO 5 groups in oxyfluoride glasses [6]. For 17 O, MAS and MQMAS spectra at 17.6 and 18.8 T have provided important new insights into structure/shift correlations in aluminosilicate zeolites [7,8] and in titanosilicate gels [9]; in oxides with somewhat lower C Q values, 17 O MAS spectra may be highly resolved at this field, dominated almost completely by chemical shift instead of second order quadrupolar line shapes [10]. For nuclides with even lower magnetogyric ratios (γ), newly available very high fields may open up whole new systems to high-resolution solid-state NMR, such as 25 Mg in silicate glasses [6].…”

Amino‐ und halogenfunktionelle Siloxititane

“…Keywords: Aminosilanol; Siloxititane; Chlorosiloxi-dititanate(IV) landiol mit Tetrachlortitan ein achtgliedriger (SiOTiO) 2 -Ring und in der Umsetzung des Diphenylsilandiol mit Tetra-n-butoxititan der Titanspirocyclus (Ti[O(Ph 2 SiO) 4 ] 2 ) [5][6][7][8][9][10]. Ersetzt man in dieser Reaktion Tetra-n-butoxititan durch Tetra-iso-propoxititan, entsteht ein achtgliedriger (SiOTiO) 2 -Ring, zwischen den beiden Titanatomen mit einer O-Si(Ph) 2 -O-Einheit überbrückt ist [11].…”