RESUMEN
Conspicuous absence: (29)SiNMR studies show that highly condensed, four-coordinate Si-containing anions are common in concentrated alkali-metal silicate solutions, but reveal no evidence for the existence of specialized zeolite building units. The results add to the mounting evidence that silicate polymerization simply proceeds through stepwise condensation of monosilicate tetrahedra.
Asunto(s)
Aniones/química , Metales Alcalinos/química , Silicatos/química , Zeolitas/química , Espectroscopía de Resonancia MagnéticaRESUMEN
Addition of cis-1,2-dihydroxycyclopentane to aqueous alkaline silicate solutions results in the spontaneous formation of three organosilicate species, each with a 2:1 ligand to Si ratio and a pentacoordinated silicon centre. By using a mixture of both cis-1,2-dihydroxycyclopentane and 1,4-anhydroerythritol we show unambiguously that all three species are diastereomers of the monomeric bis(diolato)-hydroxo complex, [(L=)(2)SiOH](-)(where L represents the cis-diol ligand), thus clarifying the general assignment of (29)Si NMR spectra reported for silicate solutions containing furanoidic sugars with vicinal cis-diol functionality, such as ribose.