Chemistry of 2,2,6,6,-Tetramethyl-3,5-heptanedione (Hthd) Modification of Zirconium and Hafnium Propoxide Precursors
| Autor: | Gerald I. Spijksma, Dave H.A. Blank, Marc Henry, Vadim G. Kessler, Andreas Fischer, Henny J.M. Bouwmeester |
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| Přispěvatelé: | Inorganic Materials Science, Faculty of Science and Technology, Inorganic Membranes |
| Rok vydání: | 2006 |
| Předmět: |
Zirconium
Inorganic chemistry chemistry.chemical_element Alcohol Crystal structure Medicinal chemistry Hafnium Inorganic Chemistry chemistry.chemical_compound symbols.namesake chemistry Proton NMR symbols IR-59196 METIS-235014 Metalorganic vapour phase epitaxy Physical and Theoretical Chemistry van der Waals force Solubility |
| Zdroj: | Inorganic chemistry, 45(13), 4938-4950. American Chemical Society |
| ISSN: | 1520-510X 0020-1669 |
| Popis: | The modification of different zirconium propoxide and hafnium propoxide precursors with 2,2,6,6,-tetramethyl-3,5-heptanedione (Hthd) was investigated by characterization of the isolated modified species. The complexes [Zr(OnPr)3(thd)](2), [Zr(OnPr)(OiPr)2(thd)]2, Zr(OiPr)(thd)3, [Hf(OnPr)3(thd)]2, and Hf(OiPr)(thd)3 were isolated and characterized. The structure of the n-propoxide analogue of Zr(OiPr)(thd)3 could not be refined, but its existence was clearly demonstrated by XRD and 1H NMR. The modification of the propoxide precursors involves mono- and trisubstituted intermediate compounds and does not involve a disubstituted compound; thus, the commercial product that is claimed to be "Zr(OiPr)2(thd)2" and is most commonly used for the MOCVD preparation of ZrO2 does not exist. No evidence was found for the presence of such a compound in either zirconium- or hafnium-based systems. Formation of the dimeric hydroxo-di-thd-substituted complex, [Hf(OH)(OiPr)(thd)2]2, which could be isolated only for hafnium-based systems, occurs on microhydrolysis. All heteroleptic intermediates are eventually transformed to the thermodynamically stable Zr(thd)4 or Hf(thd)4) The compounds obtained from isopropoxide precursors showed a higher stability than those with n-propoxide ligands or a combination of both types. In addition, it is important to note that residual alcohol facilitates the transformation and strongly enhances its rate. The unusually low solubility and volatility of MIV(thd)4 has been shown to be due to close packing and strong van der Waals interactions in the crystal structures of these compounds. |
| Databáze: | OpenAIRE |
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