Cyclopentadienyl–Silsesquioxane Titanium Catalysts: Factors Affecting Their Formation and Activity in Olefin Epoxidation with Aqueous Hydrogen Peroxide

María Ventura, Vanessa Tabernero, Tomás Cuenca, Beatriz Royo Cantabrana, Gerardo Jiménez

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Abstract

The reaction of titanium chlorosilyl-substituted cyclopentadienyl (Cp) complexes, Ti(η5-C5H3R′SiMe2Cl)Cl3(R′ = H, 1b; SiMe3, 1c), with 1 equiv. of various silsesquioxane trisilanols, R7Si7O9(OH)3(R = iBu, 2a; Ph, 2b), affords either corner-capped Cp derivatives, Ti(η5-C5H3R′SiMe2Cl)(R7Si7O123O3) (R′ = H, R = iBu, 5a, Ph, 5b; R′ = SiMe3, R = iBu, 7a, Ph, 7b), or cyclopentadienyl–silsesquioxane complexes, Ti(η5-C5H4SiMe2OR7Si7O112O2)Cl (R′ = H, R = iBu, 6a, Ph, 6b; R′ = SiMe3, R = iBu, 8a, Ph, 8b), depending on the reaction conditions. In any case, upon heating, kinetic products 5 and 7 are transformed into the corresponding thermodynamic products 6 and 8, respectively. The electron-donating ability of the Cp ring is a relevant controlling parameter: a strong π-donor character facilitates the isomerization process. In addition, the nature of the silicon substituents in the silsesquioxane framework, the type of solvent, and the reaction temperature are also factors that significantly affect this process. Cyclopentadienyl–silsesquioxane complexes 6b and 8b are efficient and selective catalysts for epoxidation with aqueous hydrogen peroxide under mild conditions. Such a catalytic efficiency is attributed to the hydrophobic environment generated about the titanium atom by the Cp ring incorporated into the cyclopentadienyl–silsesquioxane ligand.

Original languageEnglish
Pages (from-to)2843-2849
Number of pages7
JournalEuropean Journal of Inorganic Chemistry
Volume2016
Issue number17
DOIs
Publication statusPublished - 2016

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Epoxidation
Alkenes
Titanium
Hydrogen Peroxide
Catalysts
Silicon
Isomerization
Thermodynamics
Ligands
Derivatives
Heating
Atoms
Kinetics
Electrons
Temperature

Keywords

  • Cyclopentadienyl ligands
  • Epoxidation
  • Hydrogen peroxide
  • Titanasilsesquioxane
  • Titanium

Cite this

@article{17b8c3fe24694a4d8657ec605d9a9da5,
title = "Cyclopentadienyl–Silsesquioxane Titanium Catalysts: Factors Affecting Their Formation and Activity in Olefin Epoxidation with Aqueous Hydrogen Peroxide",
abstract = "The reaction of titanium chlorosilyl-substituted cyclopentadienyl (Cp) complexes, Ti(η5-C5H3R′SiMe2Cl)Cl3(R′ = H, 1b; SiMe3, 1c), with 1 equiv. of various silsesquioxane trisilanols, R7Si7O9(OH)3(R = iBu, 2a; Ph, 2b), affords either corner-capped Cp derivatives, Ti(η5-C5H3R′SiMe2Cl)(R7Si7O12-κ3O3) (R′ = H, R = iBu, 5a, Ph, 5b; R′ = SiMe3, R = iBu, 7a, Ph, 7b), or cyclopentadienyl–silsesquioxane complexes, Ti(η5-C5H4SiMe2OR7Si7O11-κ2O2)Cl (R′ = H, R = iBu, 6a, Ph, 6b; R′ = SiMe3, R = iBu, 8a, Ph, 8b), depending on the reaction conditions. In any case, upon heating, kinetic products 5 and 7 are transformed into the corresponding thermodynamic products 6 and 8, respectively. The electron-donating ability of the Cp ring is a relevant controlling parameter: a strong π-donor character facilitates the isomerization process. In addition, the nature of the silicon substituents in the silsesquioxane framework, the type of solvent, and the reaction temperature are also factors that significantly affect this process. Cyclopentadienyl–silsesquioxane complexes 6b and 8b are efficient and selective catalysts for epoxidation with aqueous hydrogen peroxide under mild conditions. Such a catalytic efficiency is attributed to the hydrophobic environment generated about the titanium atom by the Cp ring incorporated into the cyclopentadienyl–silsesquioxane ligand.",
keywords = "Cyclopentadienyl ligands, Epoxidation, Hydrogen peroxide, Titanasilsesquioxane, Titanium",
author = "Mar{\'i}a Ventura and Vanessa Tabernero and Tom{\'a}s Cuenca and Cantabrana, {Beatriz Royo} and Gerardo Jim{\'e}nez",
year = "2016",
doi = "10.1002/ejic.201501474",
language = "English",
volume = "2016",
pages = "2843--2849",
journal = "European Journal of Inorganic Chemistry",
issn = "1434-1948",
publisher = "Wiley-VCH Verlag Berlin",
number = "17",

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TY - JOUR

T1 - Cyclopentadienyl–Silsesquioxane Titanium Catalysts

T2 - Factors Affecting Their Formation and Activity in Olefin Epoxidation with Aqueous Hydrogen Peroxide

AU - Ventura, María

AU - Tabernero, Vanessa

AU - Cuenca, Tomás

AU - Cantabrana, Beatriz Royo

AU - Jiménez, Gerardo

PY - 2016

Y1 - 2016

N2 - The reaction of titanium chlorosilyl-substituted cyclopentadienyl (Cp) complexes, Ti(η5-C5H3R′SiMe2Cl)Cl3(R′ = H, 1b; SiMe3, 1c), with 1 equiv. of various silsesquioxane trisilanols, R7Si7O9(OH)3(R = iBu, 2a; Ph, 2b), affords either corner-capped Cp derivatives, Ti(η5-C5H3R′SiMe2Cl)(R7Si7O12-κ3O3) (R′ = H, R = iBu, 5a, Ph, 5b; R′ = SiMe3, R = iBu, 7a, Ph, 7b), or cyclopentadienyl–silsesquioxane complexes, Ti(η5-C5H4SiMe2OR7Si7O11-κ2O2)Cl (R′ = H, R = iBu, 6a, Ph, 6b; R′ = SiMe3, R = iBu, 8a, Ph, 8b), depending on the reaction conditions. In any case, upon heating, kinetic products 5 and 7 are transformed into the corresponding thermodynamic products 6 and 8, respectively. The electron-donating ability of the Cp ring is a relevant controlling parameter: a strong π-donor character facilitates the isomerization process. In addition, the nature of the silicon substituents in the silsesquioxane framework, the type of solvent, and the reaction temperature are also factors that significantly affect this process. Cyclopentadienyl–silsesquioxane complexes 6b and 8b are efficient and selective catalysts for epoxidation with aqueous hydrogen peroxide under mild conditions. Such a catalytic efficiency is attributed to the hydrophobic environment generated about the titanium atom by the Cp ring incorporated into the cyclopentadienyl–silsesquioxane ligand.

AB - The reaction of titanium chlorosilyl-substituted cyclopentadienyl (Cp) complexes, Ti(η5-C5H3R′SiMe2Cl)Cl3(R′ = H, 1b; SiMe3, 1c), with 1 equiv. of various silsesquioxane trisilanols, R7Si7O9(OH)3(R = iBu, 2a; Ph, 2b), affords either corner-capped Cp derivatives, Ti(η5-C5H3R′SiMe2Cl)(R7Si7O12-κ3O3) (R′ = H, R = iBu, 5a, Ph, 5b; R′ = SiMe3, R = iBu, 7a, Ph, 7b), or cyclopentadienyl–silsesquioxane complexes, Ti(η5-C5H4SiMe2OR7Si7O11-κ2O2)Cl (R′ = H, R = iBu, 6a, Ph, 6b; R′ = SiMe3, R = iBu, 8a, Ph, 8b), depending on the reaction conditions. In any case, upon heating, kinetic products 5 and 7 are transformed into the corresponding thermodynamic products 6 and 8, respectively. The electron-donating ability of the Cp ring is a relevant controlling parameter: a strong π-donor character facilitates the isomerization process. In addition, the nature of the silicon substituents in the silsesquioxane framework, the type of solvent, and the reaction temperature are also factors that significantly affect this process. Cyclopentadienyl–silsesquioxane complexes 6b and 8b are efficient and selective catalysts for epoxidation with aqueous hydrogen peroxide under mild conditions. Such a catalytic efficiency is attributed to the hydrophobic environment generated about the titanium atom by the Cp ring incorporated into the cyclopentadienyl–silsesquioxane ligand.

KW - Cyclopentadienyl ligands

KW - Epoxidation

KW - Hydrogen peroxide

KW - Titanasilsesquioxane

KW - Titanium

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U2 - 10.1002/ejic.201501474

DO - 10.1002/ejic.201501474

M3 - Article

VL - 2016

SP - 2843

EP - 2849

JO - European Journal of Inorganic Chemistry

JF - European Journal of Inorganic Chemistry

SN - 1434-1948

IS - 17

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