Site-Isolated Pt-SBA15 Materials from Tris(tert-butoxy)siloxy Complexes of Pt(II) and Pt(IV)

Abstract

Two novel tris(tert-butoxy)siloxy complexes of Pt(II) and Pt(IV) were prepared in high yields, (cod)Pt[OSi(O t Bu)3]2 (1; 87%; cod = 1,5-cyclooctadiene) and Me3Pt(tmeda)[OSi(O t Bu)3] (2; 81%; tmeda = N,N,N′,N′-tetramethylethylenediamine). The structures of these compounds were determined by multinuclear NMR spectroscopy and by single-crystal X-ray analysis. The thermolytic chemistry of 1 and 2 in the solid state was studied by thermogravimetric analysis. The thermal decomposition of these complexes resulted in the formation of Pt metal, with the elimination of HOSi(O t Bu)3. Precursors 1 and 2 react with the surface Si−OH groups of mesoporous SBA15 silica to generate surface-supported Pt centers. The coordination environments of the supported Pt centers in these new materials, termed Pt(II)SBA15 and Pt(IV)SBA15, were investigated using Fourier-transform infrared spectroscopy, X-ray absorption near-edge spectroscopy, and extended X-ray absorption fine structure analysis. These materials were also characterized using N2 porosimetry, powder X-ray diffraction and transmission electron microscopy. Comparisons with the molecular precursors 1 and 2 revealed many similarities, and the results are indicative of isolated Pt(II) and Pt(IV) centers. In addition, isolated Pt centers proved to be robust in inert atmosphere to 150−200 °C, which is similar to the decomposition temperatures of 1 and 2.

Synthesis of Different CeO2 Structures on Mesoporous Silica and Characterization of Their Reduction Properties

“…Mesoporous silicas-MCM-41 and SBA-15-were used as the supports. Previous work has shown that high dispersion of V, 59 Pt, 60 and Ti 61 species can be deposited by using Under inert atmosphere, the moisture-sensitive compounds Ce(O i Pr) 4 and Ce(O t Bu) 4 were dissolved in toluene that had been dried over CaH 2 . These precursors dissolved rapidly at room temperature, yielding a bright yellow solution in the case of Ce(O t Bu) 4 and a honey-colored solution in the case of Ce-(O i Pr) 4 .…”

Siloxyaluminate and Siloxygallate Complexes as Models for Framework and Partially Hydrolyzed Framework Sites in Zeolites and Zeotypes

“…As such, the Fourier‐transformed magnitude images and un‐transformed images for 6 , 7 , 10 , and 11 are provided in the supplementary information (see the Supporting Information). In general, isolated molecular complexes have previously served as models for the identification of structurally complex species on silica surfaces, so this data should be of use to the zeolite community [20, 29, 97–101] …”

“…In general, isolated molecular complexes have previously served as modelsf or the identification of structurally complex specieso ns ilica surfaces, so thisd ata should be of use to the zeolite community. [20,29,[97][98][99][100][101] Reactivity of complexes 10 and 11 with relevancefor Meerwin-Pondorf-Verley transfer hydrogenation over supported group-13m etal catalysts…”

Rare Earth Doped Silica Nanoparticles via Thermolysis of a Single Source Metallasilsesquioxane Precursor

“…siloxanes or siloxides) in the presence of a silica or alumina support111213141516. Thermolysis of inorganic molecules and clusters has also been shown to yield nanostructured materials1718.…”

“…Heating to 900 °C resulted in the formation of a black tar-like material, with <30% of total mass remaining, indicating significant compound degradation at this temperature. Previously, Tilley and co-workers have demonstrated that decomposition of single-source precursors (siloxy compounds) can occur at ~150 °C and can efficiently produce homogeneous metal-silica (bulk) materials1215. With this in mind, and considering the thermal profile of compound 1 described above, thermolysis experiments were carried out at 300 °C under a nitrogen atmosphere (see Methods) and the resulting white powder was collected for analysis.…”