Synthesis and structure of functional spherosilicate building block molecules for materials synthesis

119Sn NMR chemical shift tensors in anhydrous and hydrated Si8O20(SnMe3)8 crystals

“…Four tin resonances (147, 136, 58, and −32 ppm; integrated intensity = 1 : 1 : 1 : 1) are observed, one for each of the distinct tin sites seen in the XRD of this material. [3] The span and skew of the two sharp high-frequency resonances are similar to the signal observed in the NMR spectrum of 1 (Table 1.) Indeed, the single crystal X-ray structure of 2 shows two tin sites, Sn-1 and Sn-4, with distorted tetrahedral geometries (average angles of OSn-C at sites are 102.4 and 103.7…”

“…1, all NMR parameters are summarized in Table 1 • , respectively. [3] The resonance asymmetry shows the degree of sensitivity of the tin chemical shift resonance to changes in geometry. It also demonstrates that the molecule does not show dynamic disorder in the crystal that would average the tin resonances.…”

“…Each of the oxygen atoms linking trimethyl tin groups to the cubic silicate cage are hydrogen bonded to water molecules. [3] Furthermore, the oxygen atoms of water molecules are within weak bonding distance to two of the four unique tin atoms, Sn-2 and Sn-3 in the unit cell. Dotted lines highlight the bonding interactions between water and the OSnMe moieties in the illustration.…”

“…[2] X-ray diffraction (XRD) is a powerful tool to clarify the crystal structures of these materials. [3] Solid-state magic angle spinning (MAS) NMR spectroscopy is a sensitive tool in revealing local structural order, e.g. bonding configuration, and is complimentary to XRD methods.…”

“…The syntheses and crystal structures of 1 and 2 were reported in a previous study. [3] Compound 3 was prepared by heating compound 2 to 373 K under vacuum overnight. The amorphous structure of 3 prevents the acquisition of crystal data.…”