Surface Organometallic Chemistry of Titanium:  Synthesis, Characterization, and Reactivity of (⋮Si−O)nTi(CH2C(CH3)3)4-n (n = 1, 2) Grafted on Aerosil Silica and MCM-41

Bini, Fabien; Rosier, Cécile; Saint‐Arroman, Romain Petroff; Neumann, Eva; Dablemont, Céline; Mallmann, Aimery De; Lefèbvre, Frédéric; Niccolaï, Gerald P.; Basset, Jean‐Marie; Crocker, Mark; Buijink, Jan-Karel F.

doi:10.1021/om050675g

Cited by 42 publications

(45 citation statements)

References 78 publications

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“…A similar reactivity was reported for 70 several organometallic complexes of general formula X x ML n (where M = transition metal, X = halogen and L = ligand) that were found to react with surface silanols ≡SiOH of highly dehydroxylated silica to yield ≡SiOMX x-1 L n species along with HX. 1,3,4,[24][25][26][27] For tetrahedral X x ML n complexes, the grafting 75 process usually occurs without major changes in terms of structure and geometry of the grafted fragment, that is tetrahedral d 0 ML 4 complexes remain mostly tetrahedral upon grafting for a large range of metals.…”

Section: Introductionmentioning

confidence: 99%

Silica-supported Ti chloride tetrahydrofuranates, precursors of Ziegler–Natta catalysts

et al. 2013

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The structural and electronic properties of silica-supported titanium chloride tetrahydrofuranates samples, obtained by impregnating a polymer-grade dehydroxylated silica with TiCl 4 (thf) 2 and TiCl 3 (thf) 3 complexes, precursors of Ziegler-Natta catalysts, are investigated by means of FT-IR, XAS, XES and diffuse reflectance UV-Vis spectroscopy, coupled with DFT calculations. The properties of the two silicasupported samples are very similar, irrespective of the starting precursor. In both cases, most of the 10 chlorine ligands originally surrounding the Ti sites are substituted by oxygen ligands upon grafting on silica. As a consequence, the electronic properties of silica-supported Ti sites are largely different from those of the corresponding precursors, and in both cases most of the grafted Ti sites have a formal oxidation state of +4. The whole set of experimental data provide evidence that mono-nuclear Ti species are mainly present at the silica surface.

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Section: Introductionmentioning

confidence: 99%

Silica-supported Ti chloride tetrahydrofuranates, precursors of Ziegler–Natta catalysts

et al. 2013

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“…[7] An absorption maximum between 210 and 230 nm is generally interpreted as indicative of isolated, 4-coordinate titanium centers in crystalline silicate matrices. Band maxima between 230 and 250 nm indicate either presence of isolated titanium atoms with higher coordination numbers or small nanometer sized polynuclear Ti x O y domains.…”

Section: Resultsmentioning

confidence: 99%

“…[7] Rigorous, well defined tetrahedral symmetry frequently leads to very narrow, intense preedge features while octahedral symmetry gives rise to multiple bands with much lower intensities. The XANES data for the 2C-, 3C-, 4C-Ti catalysts are consistent with 4-or 5-coordinate Ti centers.…”

Section: Resultsmentioning

confidence: 99%

“…[7] In general, Si 8 O 12 (OSnMe 3 ) 8 and SiCl 4 py 2 are transferred to a Schlenk reaction vessel followed by the addition of approximately 30 mL of toluene. The solution is stirred at 80°C under static vacuum for up to 24 hours whereupon all volatiles (solvent, trimethyltin chloride, pyridine) are removed under vacuum.…”

Section: General Synthesis Of Nanostructured Silicate Building Block mentioning

confidence: 99%

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Nanostructured Metal Oxide Catalysts via Building Block Syntheses

Barnes¹

2013

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Executive Summary:A broadly applicable methodology has been developed to prepare new single site catalysts on silica supports. This methodology requires of three critical components: a rigid building block that will be the main structural and compositional component of the support matrix; a family of linking reagents that will be used to insert active metals into the matrix as well as cross link building blocks into a three dimensional matrix; and a clean coupling reaction that will connect building blocks and linking agents together in a controlled fashion. The final piece of conceptual strategy at the center of this methodology involves dosing the building block with known amounts of linking agents so that the targeted connectivity of a linking center to surrounding building blocks is obtained. Achieving targeted connectivities around catalytically active metals in these building block matrices is a critical element of the strategy by which single site catalysts are obtained. This methodology has been demonstrated with a model system involving only silicon and then with two metal-containing systems (titanium and vanadium). The effect that connectivity has on the reactivity of atomically dispersed titanium sites in silica building block matrices has been investigated in the selective oxidation of phenols to benezoquinones. 2-connected titanium sites are found to be five times as active (i.e. initial turnover frequencies) than 4-connected titanium sites (i.e. framework titanium sites). Accomplishments: Proposed:In the work supported by the BES program of the DOE we proposed to develop a methodology to prepare nanostructured complex oxide catalysts. There were three specific objectives to this research program:1. To develop a general, broadly applicable synthetic methodology to prepare single site catalysts in a targeted fashion. 2. To obtain high densities of these sites on the support materials while maintaining strict site isolation. 3. To accomplish (1) and (2) on a porous, high surface area support with a distributed pore system composed of macro, meso and micropores to obtain high numbers of sites on a per unit mass or volume basis for the material. 4. To study the activity of these new nanostructured materials as catalysts in selective oxidation reactions.3 Actual:1. During an early phase of this research project objectives (1) and (2) were demonstrated and described for a model system (containing no active catalysis centers) in a publication that is given at the end of this technical report.[1] 2. This study was followed up by more detailed investigations involving titanium and vanadyl centers in silica building block matrices. The results of this work were recently reported in several publications given at the end of this technical report.[2-4] 3. More recently we have completed two additional studies focusing on how the porosity of these matrices changes with the synthetic stoichiometry used in their synthesis and the activity of single site titanosilicate catalysts in the selective oxidation of phenols...

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“…The grafting reaction of tetraneopentyl titanium was also studied on MCM-41 materials [30][31][32]. Here again the structure of the MCM-41 material led to the formation of multigrafted species rather than monografted ones.…”

Section: Grafting Reactions Of Organometallic Complexes On Mesoporousmentioning

confidence: 99%

Modification of the adsorption and catalytic properties of micro- and mesoporous materials by reactions with organometallic complexes

et al. 2010

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This review describes the work of two laboratories in the field of the modification of micro-and mesoporous molecular sieves through reactions with organometallic complexes. The modification of zeolites can occur inside the pore channels or on the external surface, depending on the size of the organometallic complex. When the modification occurs on the external surface, it results in a decrease of the pore entrance, which will lead in turn to a modification of the sorption properties of the zeolite, by decreasing the rate of the adsorption (mainly by a kinetic control). Such a material can be also used in catalysis, because the external acid sites, which are responsible for side-reactions, have been removed upon grafting. When small organometallic complexes are used, they can fill the channels and cages of the zeolite and react with internal hydroxyl groups. Due to the high acidity of zeolites, the reaction occurs very easily (for example at 100 °C on faujasite), in contrast to what is observed on the external surface, therefore leading to high metal loadings. In that case, the modification of the sorption properties will be mainly related to a thermodynamic control. The resulting materials can be useful in catalysis, by combining the activity of the organometallic complex and properties (for example shape-selectivity) of the zeolite. Modification of mesoporous molecular sieves occurs always in the pores and results in altering of the sorption properties of the solid, by changing the interaction type between the sorbent and the sorbate. For example the sorption isotherm of alkanes is changed from type II to type III according to the IUPAC nomenclature. zeolites, transition metals, organometallic compounds, adsorption properties

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Surface Organometallic Chemistry of Titanium: Synthesis, Characterization, and Reactivity of (⋮Si−O)_nTi(CH₂C(CH₃)₃)₄_-_n (n = 1, 2) Grafted on Aerosil Silica and MCM-41

Cited by 42 publications

References 78 publications

Silica-supported Ti chloride tetrahydrofuranates, precursors of Ziegler–Natta catalysts

Silica-supported Ti chloride tetrahydrofuranates, precursors of Ziegler–Natta catalysts

Nanostructured Metal Oxide Catalysts via Building Block Syntheses

Modification of the adsorption and catalytic properties of micro- and mesoporous materials by reactions with organometallic complexes

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