Tripodal Tetrahedral Titanium Coordination in the Silica-Grafted Titania Epoxidation Catalysts: Is Not It Only a Myth? Selective Formation of [Cy₇Si₇O₁₂Ti]₂(μ-OR)₂(μ-ROH) Cores on Thermal “Dissociation” of Alkoxytitanasilsesquioxanes

Abstract

The molecular structures of the species crystallizing from solutions of alkoxytitanasilsesquioxanes in hydrocarbons upon reflux confirm the partial release of solvating alcohol. They feature, however, distinctly the formation of a dinuclear core with preserved hexacoordination for the metal atoms. The active titanium centers in the silica-titania epoxidation catalysts, lacking the sterically demanding ligands, are thus quite probably also hexacoordinated.

Mixed‐Ligand Titanium “Oxo Clusters”: Structural Insights into the Formation and Binding of Organic Molecules and Transformation into Oxide Nanostructures on Hydrolysis and Thermolysis

“…Understanding that oxo complexes are true precursors of oxide materials, and that they are potential models for the nucleation of oxide phases in the sol–gel process, as well as being models for the surface structure of oxide particles, has become one of the strongest sources of recent interest regarding the structure and reactivity of these compounds. Valuable insights have been obtained into the structure of heterogeneous titania‐based catalysts and into the surface structure and reactivity of hybrid TiO 2 ‐based adsorbents . A new source of interest in oxo complexes emerged with the works of Tshuva et al, demonstrating the bioactivity and anti‐inflammatory and cytostatic effects of the phenoxide complexes of titanium , .…”

Straightforward synthesis and structural characterization of the first alkoxy-zircono-silsesquioxanes — Potential models for zirconia–silica epoxidation catalysts

“…They offer, on the other hand, an approach (through thermal decomposition or polymerization of the organic residues) to complex inorganic or hybrid materials with attractive mechanical and optical properties [7,8]. Strong effort has been made in the synthesis and structural characterization of rare earth [8] and titanium [9,10] silsesquioxane derivatives. The chemistry of the silsesquioxane complexes of zirconium, in spite of the perspectives of their application in both materials synthesis and catalysis, remained rather poorly explored: the interaction of zirconium alkoxides with siloxane cages has not been reported, while the interaction of (PhCH 2 ) 2 [11].…”

“…In its mass-spectrum the first fragment, m/z= Major difference in the nature of cyclo-hexyl and cyclo-pentyl derivatives obtained in this work was the absence of interstitial hexane solvent in the structure of 4 and also the presence of only one solvating alcohol ligand per dinuclear zirconium-alkoxide unit (as confirmed by NMR). The formation of hemi-solvates has recently been envisaged structurally for the titanium silsesquioxane derivatives [10].…”

Multinuclear Clusters of Manganese and Lithium with Silsesquioxane-Derived Ligands: Synthesis and Ligand Rearrangement by Dioxygen- and Base-Mediated Si–O Bond Cleavage

“…In another study from Riollet et al, the silsesquioxane ligand was studied as a model of a silica-surface-templated active heterogeneous catalytic species . Among other first-row d-block metal complexes of silsequioxanes, titanium, − iron, − vanadium, − and zinc ,− are most common, although there are examples with cobalt, − chromium, ,, and copper ,− and one with scandium . We report here the synthesis of multinuclear manganese complexes of POSS-derived ligands via the reaction of Mn­(N­(SiMe 3 ) 2 ) 2 and 1,3,5,7,9,11,14-heptaphenyl-2,4,6,8,10,12,13,15,16-nonaoxa-1,3,5,7,9,11,14-heptasilatricyclo­[7.3.3.15,11]­hexadecane-3,7,14-triol [Ph 7 Si 7 O 9 (OH) 3 , (L1)­H 3 ] and (2 S ,4 S ,6 S ,8 S )-2,4,6,8-tetraphenyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane-2,4,6,8-tetraol [Ph 4 Si 4 O 4 (OH) 4 , (L2)­H 4 ].…”