Soluble Aluminosilicates with Frameworks of Minerals

Montero, Mavis L.; Voigt, Andreas; Teichert, Markus; Usón, Isabel; Roesky, Herbert W.

doi:10.1002/anie.199525041

Cited by 79 publications

(38 citation statements)

References 20 publications

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“…Similar increases in Si NMR shieldings have been calculated for the formation of single 3-and 4-rings from H 2 Si(OH)2 monomers and have been shown to be in good agreement with experimental data. 19 For unstrained rings (4-rings or larger) the shielding increase appears to be generally about 8-9 ppm for every Si-O-H group converted to Si-O-Si.…”

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confidence: 76%

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Calculation of the Structural, Energetic, and Spectral Properties of Alumoxane and Aluminosilicate “Drum” Molecules

Tossell

1998

Inorg. Chem.

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In aluminosilicate cage compounds Al-O-Al linkages are usually not found, in accord with the "Al avoidance" rule. In some cases Al-O-Al linkages can be stabilized by forming additional bonds to the bridging O atom. This can occur through direct coordination of cations or by the fusing of aluminosilicate rings to create "drum"-like molecules. We have calculated the structures, energetics, and NMR and vibrational spectra for several such aluminosilicate drum-like molecules and for related alumoxanes, as well as for analogous silicate molecules. Calculations on Si(2)Al(4)O(6)H(8), Al(6)O(6)H(6), Si(4)Al(4)O(8)H(12), Si(6)O(9)H(6), Si(8)O(12)H(8), Si(4)Al(4)O(12)H(8)(4)(-), and Si(4)Al(4)O(12)H(8)Na(4) reproduce the experimental structures (where available) and the observed trends in Si NMR shieldings. In the double 3-ring and double 4-ring (D3R and D4R) silicate cages Si(6)O(9)H(6) and Si(8)O(12)H(8) the Si atoms are shielded compared to their monomeric units, with a significantly greater shielding for the D4R compared to the D3R. The Si(4),Al(4) D4R bare anion has about the same Si shielding as Si(8)O(12)H(8), while the neutral Si(4)Al(4)O(12)H(8)Na(4) shows a 13 ppm deshielding. These trends in Si NMR shieldings are in accord with those observed in both the molecules and in aluminosilicate minerals. On the other hand, the fused or "drum"-like D3R and D4R rings show Si atoms and Al atoms which are calculated to be deshielded with respect to their corresponding monomers, in accord with experiment. We also reproduce the difference in frequency of the most intense IR absorptions for the various double-ring molecules. While silicate D4R cages are considerably more stable than corresponding D3R, the stabilities of the D3R molecule Al(6)O(6)H(6) and the hypothetical D4R symmetry Al(8)O(8)H(8) are quite similar. Calculated gas-phase proton affinities for Si(6)O(9)H(6), Si(2)Al(4)O(6)H(8), and Al(6)O(6)H(6) are similar, although protonation causes cage breaking for Si(2)Al(4)O(6)H(8) and Al(6)O(6)H(6). For a drum-like D4R of composition Si(4)Al(4)O(8)H(12), which is calculated to be stable with respect to Si(2)Al(4)O(6)H(8) and Si(4)O(4)H(8), we present a calculated structure as well as NMR properties.

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confidence: 76%

“…[1][2][3] Such compounds are interesting for a number of reasons. First, they make it possible to establish whether the principles determinining structural stability are the same in molecular and mineral aluminosilicates.…”

Section: Introductionmentioning

confidence: 99%

Calculation of the Structural, Energetic, and Spectral Properties of Alumoxane and Aluminosilicate “Drum” Molecules

Tossell

1998

Inorg. Chem.

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“…We have not considered all of the possible isomers of this molecule, but have rather concentrated upon (1) We have also studied some of the possible geometries of the Si 4 Al 4 O 12 H 8 Na 4 and Si 4 Al 4 O 12 H 12 molecules. An alternating isomer of Si 4 Al 4 O 12 H 8 Na 4 with Na + ions near the centers of four faces of the T 8 cube has a calculated geometry very much like that determined by Montero et al 32 (and is found to be more stable than the S 4 symmetry isomer in which the Na + are tetrahedrally disposed). The isomer with four Al-O-Al bonds localized in one of the four-atom rings and with Na + bound to each of these Al-O-Al bridges is less stable by 344 kJ/mol.…”

Section: Resultsmentioning

confidence: 73%

Theoretical Studies of Si and Al Distributions in Molecules and Minerals with Eight Tetrahedrally Coordinated Atoms (T₈) in Double-Four-Ring (D4R) Geometries: Octasilasesquioxanes, Gismondite, and Zeolite A

Tossell

1996

J. Phys. Chem.

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The inorganic compound octasilasesquioxane, Si 8 O 12 H 8 , the mineral gismondite, CaSi 2 Al 2 O 8 ‚4H 2 O, and synthetic Linde zeolite A all contain structural units in which eight tetrahedrally coordinated atoms (T 8 , T ) Si and/or Al) and their bridging oxygens form a double-four-ring (D4R) geometry. D4R compounds are much more stable than the single four rings that occur in some crystalline silicates and silicate glasses, since hydrolysis by nucleophilic attack at the T-atom is hindered by the cage geometry. Recently techniques have been developed for systematically incorporating non-Si-atoms into such T 8 units. We have calculated equilibrium geometries by using Hartree-Fock self-consistent-field molecular orbital methods and 6-31G* basis sets for Si 8 O 12 H 8 , Si 8 O 12 (OH) 8 , and a number of related molecules. Vibrational spectra have been calculated for Si 8 O 12 H 8 , Si 8 O 20 8-, and the stable "alternating" isomer of the Si 4 Al 4 O 12 H 8 4-anion, which contains only Si-O-Al bridges. The calculated vibrational spectra for Si 8 O 12 H 8 are in good agreement with those measured, and the assignment of the spectra to the various normal modes is consistent with earlier models based on empirical force fields. Several other "paired" isomeric forms of Si 4 Al 4 O 12 H 8 4-, which contain some Al-O-Al bridges, are found to be higher in energy than the alternating structure, in accordance with Loewenstein's rule. However, the energies of the Si 4 Al 4 O 12 H 8 4-isomers depend upon the spatial separation of the Al-O-Al bridges as well as upon their number. For the Si 6 Al 2 O 12 H 8 2-anion, we have evaluated the stability of three different isomers in which the two Al-atoms are separated by increasing numbers of bonds. We find the lowest energy for the structure with a maximum separation of the Al-atoms, in accordance with Dempsey's rule. The energy penalty for the presence of Al-O-Al bridges is very similar in magnitude to that previously calculated in single-four-ring compounds. However, the relative energies of the various isomers of the

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“…The idea that molecular clusters can capture the key chemistry at mineral functional groups is actually quite old. A few visionaries were trying to make this point many years ago, [9,10] but only recently has this idea found a receptive audience. [11][12][13] In this article we review some of research that employs these clusters as guides for interfacial reactions and hydrolytic processes.…”

Section: Introductionmentioning

confidence: 97%

Minerals as Molecules—Use of Aqueous Oxide and Hydroxide Clusters to Understand Geochemical Reactions

Casey

Rustad

Spiccia

2009

Chemistry A European J

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Large aqueous oxide ions as minerals! Minerals dissolve by repeated ligand exchange reactions and geochemists use polyoxometalate ions to establish structure-reactivity relations for environmentally important functional groups. Here, for example, are plotted the dissolution rates of two classes of minerals against rates of solvent exchanges around the corresponding aquo ions.Geochemists and environmental chemists make predictions about the fate of chemicals in the shallow earth over enormously long times. Key to these predictions is an understanding of the hydrolytic and complexation reactions at oxide mineral surfaces that are difficult to probe spectroscopically. These minerals are usually oxides with repeated structural motifs, like silicate or aluminosilicate polymers, and they expose a relatively simple set of functional groups to solution. The geochemical community is at the forefront of efforts to describe the surface reactivities of these interfacial functional groups and some insights are being acquired by using small oligomeric oxide molecules as experimental models. These small nanometer-size clusters are not minerals, but their solution structures and properties are better resolved than for minerals and calculations are relatively well constrained. The primary experimental data are simple rates of steady oxygen-isotope exchanges into the structures as a function of solution composition that can be related to theoretical results. There are only a few classes of large oxide ions for which data have been acquired and here we review examples and illustrate the general approach, which also derives directly from the use of model clusters to understand for the active core of metalloenzymes in biochemistry.

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Soluble Aluminosilicates with Frameworks of Minerals

Cited by 79 publications

References 20 publications

Calculation of the Structural, Energetic, and Spectral Properties of Alumoxane and Aluminosilicate “Drum” Molecules

Calculation of the Structural, Energetic, and Spectral Properties of Alumoxane and Aluminosilicate “Drum” Molecules

Theoretical Studies of Si and Al Distributions in Molecules and Minerals with Eight Tetrahedrally Coordinated Atoms (T₈) in Double-Four-Ring (D4R) Geometries: Octasilasesquioxanes, Gismondite, and Zeolite A

Minerals as Molecules—Use of Aqueous Oxide and Hydroxide Clusters to Understand Geochemical Reactions

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Soluble Aluminosilicates with Frameworks of Minerals

Cited by 79 publications

References 20 publications

Calculation of the Structural, Energetic, and Spectral Properties of Alumoxane and Aluminosilicate “Drum” Molecules

Calculation of the Structural, Energetic, and Spectral Properties of Alumoxane and Aluminosilicate “Drum” Molecules

Theoretical Studies of Si and Al Distributions in Molecules and Minerals with Eight Tetrahedrally Coordinated Atoms (T8) in Double-Four-Ring (D4R) Geometries: Octasilasesquioxanes, Gismondite, and Zeolite A

Minerals as Molecules—Use of Aqueous Oxide and Hydroxide Clusters to Understand Geochemical Reactions

Contact Info

Product

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Theoretical Studies of Si and Al Distributions in Molecules and Minerals with Eight Tetrahedrally Coordinated Atoms (T₈) in Double-Four-Ring (D4R) Geometries: Octasilasesquioxanes, Gismondite, and Zeolite A