[TMPA]4[Si8O20] · 34 H2O and [DDBO]4[Si8O20] · 32 H2O are heteronetwork clathrates with 1,1,4,4-tetramethylpiperazinium (TMPA) and 1,4-dimethyl-1,4-diazoniabicyclo[2.2.2]octane (DDBO) guest cations |
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Authors: | Michael Wiebcke Jrg Emmer Jürgen Felsche Dagobert Hoebbel Günter Engelhardt |
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Institution: | Michael Wiebcke,Jörg Emmer,Jürgen Felsche,Dagobert Hoebbel,Günter Engelhardt |
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Abstract: | TMPA]4Si8O20] · 34 H2O ( 1 ) and DDBO]4Si8O20] · 32 H2O ( 2 ) have been prepared by crystallization from aqueous solutions of the respective quaternary alkylammonium hydroxide and SiO2. The crystal structures have been determined by single-crystal X-ray diffraction. 1 : Monoclinic, a = 16.056(2), b = 22.086(6), c = 22.701(2) Å, β = 90.57(1)° (T = 210 K), space group C2/c, Z = 4. 2 : Monoclinic, a = 14.828(9), b = 20.201(7), c = 15.519(5) Å, β = 124.13(4)° (T = 255 K), space group P21/c, Z = 2. The polyhydrates are structurally related host-guest compounds with three-dimensional host frameworks composed of oligomeric Si8O20]8? anions and H2O molecules which are linked via hydrogen bonds. The silicate anions possess a cube-shaped double four-ring structure and a characteristic local environment formed by 24 H2O molecules and six cations (TMPA, C8H20N2]2+, or DDBO, C8H18N2]2+). The cations themselves reside as guest species in large, irregular, cage-like voids. Studies employing 29Si NMR spectroscopy and the trimethylsilylation method have revealed that the saturated aqueous solutions of 1 and 2 contain high proportions of double four-ring silicate anions. Such anions are also abundant species in the saturated solution of the heteronetwork clathrate DMPI]6Si8O18(OH)2] · 48.5 H2O ( 3 ) with 1,1-dimethylpiperidinium (DMPI, C7H16N]+) guest cations. |
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Keywords: | Silicate hydrate 1 1 4 4-tetramethylpiperazinium 1 4-dimethyl-1 4-diazoniabicyclo[2 2 2]octane 1 1-dimethylpiperidinium clathrate crystal structure double four-ring silicate anion hydrogen bonding |
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