5-Coordinate Si Compounds as Intermediates in the Synthesis of Silicates in Nonaqueous Media

Abstract

Sodium silicoglycolate, an organosilicon compound in which silicon is in 5-coordination with respect to oxygen, is shown to be a reaction intermediate in the synthesis of a purely siliceous sodalite with ethylene glycol as solvent. The presence of silicon-29 nuclear magnetic resonances at -105.5 +/- 0.3 parts per million in solution and -102.7 parts per million in the solid state as well as x-ray powder diffraction patterns demonstrate that 5-coordinate silicon is intimately involved in the synthesis. Silicon compounds of the 5-coordinate type are highly reactive and are promising starting materials for the synthesis of novel silicone polymers, molecular sieves, glasses, semiconductors, and ceramics. We have used sodium silicoglycolate to prepare the molecular sieve silicalite as well as sodalites of different compositions.

Calculation of 29Si NMR shifts of silicate complexes with carbohydrates, amino acids, and muhicarboxylic acids: potential role in biological silica utilization

“…b Matches experimentally observed peaks at Ϫ101 ppm. c Herreros et al (1994a). d Matches experimentally observed peaks at Ϫ141 to Ϫ145 ppm.…”

Theoretical study of a five-coordinated silica polymorph

“…[30][31][32] It has also been speculated to be an important species in the synthesis of siliceous molecular sieves. 37,38 Thus, although V Si is suspected in high-pressure silicates and may form part of the network of high-pressure amorphous phases, and hypothesized in high-temperature SiO 2 -rich melts or glasses, no crystalline phases of silica containing V Si have yet been observed. The synthesis of a crystalline phase of SiO 2 entirely composed of SiO 5 units would thus be of interest from the point of view of solid-state physics and chemistry, geophysics, and materials science.…”

Designed Single‐Step Synthesis, Structure, and Derivative Textural Properties of Well‐Ordered Layered Penta‐coordinate Silicon Alcoholate Complexes

“…29 Si magic angle spinning nuclear magnetic resonance (MAS NMR) (Figure 3 A) reveals two distinct [5] Si resonances located at -105 and -108 ppm further supporting the assignment of two crystallographic Si sites. [2,3a,4] The 13 C{ 1 H} MAS NMR spectrum (Figure 3 B) shows two well-resolved regions which can be assigned to the ethylene glycolate (63 ppm) and methanolate (53 ppm) ligands. [24] The carbon ratio between the glycolate and methanolate sites using both direct excitation and cross polarization (CP) gives ca .…”