The structure of aqueous pentaoxo silicon complexes with cis-1,2-dihydroxycyclopentane and furanoidic vicinal cis-diols

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.