Surface Organometallic Chemistry of Hf(CH2tBu)4 on Silica and Silica−Alumina: Reaction of the Resulting Grafted Hafnium Neopentyl with Dihydrogen
| Autor: | Marco Delgado, Anne Baudouin, Catherine C. Santini, François Bayard, Géraldine Tosin, Jean-Marie Basset |
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| Rok vydání: | 2010 |
| Předmět: |
Surface (mathematics)
Hydrogen 010405 organic chemistry Organic Chemistry Cationic polymerization chemistry.chemical_element 010402 general chemistry 01 natural sciences 0104 chemical sciences Hafnium Inorganic Chemistry chemistry.chemical_compound chemistry Organic chemistry Physical chemistry Physical and Theoretical Chemistry Organometallic chemistry Fumed silica |
| Zdroj: | Organometallics. 29:1312-1322 |
| ISSN: | 1520-6041 0276-7333 |
| Popis: | [Hf(CH2tBu)4], 1, has been found to react at room temperature with an aerosil silica dehydroxylated at different temperatures θ (θ = 800, 500, 200 °C) to give a modified surface referred to as 1/SiO2-(θ) and with a silica−alumina to give a modified surface referred to as 1/SiO2−Al2O3-(500). With SiO2-(800) a single-site monosiloxy surface complex [(≡SiO)Hf(CH2tBu)3], 1-SiO2-(800), is obtained. Contrarily, with SiO2-(500) a monosiloxy 1-SiO2-(500) and a bis-siloxy surface complex [(≡SiO)2Hf(CH2tBu)2], 2-SiO2-(500), are formed in a ratio of 70%:30%. With SiO2-(200), there is mainly the formation of the bis-siloxy surface complex (up to 90%) but in different local environments: (≡SiO)2Hf(CH2tBu)2, 2-SiO2-(200), and (≡SiO)2(≡SiOH)Hf(CH2tBu)2, 2′-SiO2-(200). Finally with SiO2−Al2O3-(500), two major neutral surface complexes are formed: the monosiloxy 1-SiO2−Al2O3-(500) and the bisiloxy 2-SiO2−Al2O3-(500), as well as a third complex, 3, which is not as well-defined and may be cationic. Under hydrogen at 150 °C,... |
| Databáze: | OpenAIRE |
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