Siloxanes, alumoxanes and alumosiloxanes as models for surface defects in hydrolysis and condensation reactions


Subject of the project is to study hydrolysis and condensation processes at strained siloxane, alumoxane and alumosiloxane compounds. The latter can be considered to be model com-pounds for defect structures at silicate or aluminosilicate surfaces. They will be prepared by oxygenation of subvalent silicon, aluminium and aluminium/silicon compounds on using triplet or singlet O2 as well as oxygenation agents such as N2O or acetone peroxide. Conceivable target structures are edge-sharing siloxane and alumosiloxane tetrahedra, Si-O-O-Si peroxo moieties and Al-O-Al linkages. Subsequently, hydrolysis and condensation reactions at the oxygenated species with water and silanols will be investigated. We aim to monitor elementary steps in situ by mass spectrometry (A05) and 1H, 2H, 29Si, 27Al and 17O NMR as well as IR and Raman spectroscopy. Larger assemblies will also be studied by MAS NMR (C01). The investigations will be accompanied by DFT calculations on the structure, on IR and Raman data as well as on NMR chemical shifts of the model compounds (A03). In addition, highly sensitive species will be characterized by Liquid Injection Field Desorption/Ionization (LIFDI) Mass Spectrometry.


Principal Investigators
Braun, Thomas Prof. Dr. (Details) (Inorganic Chemistry)

Duration of Project
Start date: 04/2014
End date: 12/2017

Research Areas
Anorganische Chemie

Publications
A. C. Stelzer, P. Hrobárik, T. Braun, M. Kaupp, B. Braun-Cula, Inorg. Chem. 2016, 55, 4915-4923.
"Completing the Heterocubane Family [Cp*AlE]4 (E = O, S, Se, and Te) by Selective Oxygenation and Sulfuration of [Cp*Al]4: Density Functional Theory Calculations of [Cp*AlE]4 and Reactivity of [Cp*AlO]4 toward Hydrolysis"

P. Roesch, U. Warzok, M. Enke, R. Müller, C. Schattenberg, C. A. Schalley, M. Kaupp, T. Braun, P. Wittwer, Chem. Eur. J. 2017, 23, 13964-13972.
"Reactivity of the Sterically Demanding Siloxanediol Mes2Si(OH)-(μ-O)Si(OH)Mes2 Towards Water and Ether Molecules"

K. S. Lokare, P. Wittwer, B. Braun-Cula, N. Frank, S. Hoof, T. Braun, C. Limberg, Z. Anorg. Allg. Chem. 2017, 643, 1581-1588.
"Mimicking Base Ineraction with Acidic Sites [Si-O(H)-Al] of Zeolites in Molecular Models"

Last updated on 2021-06-01 at 15:27