Synthesis and Structural Characterization of a Family of Modified Hafnium tert-Butoxide for Use as Precursors to Hafnia Nanoparticles

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• 作者：Timothy J. Boyle ; Leigh Anna M. Steele ; Patrick D. Burton ; Sarah M. Hoppe ; Chelsea Lockhart ; Mark A. Rodriguez
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：November 19, 2012
• 年：2012
• 卷：51
• 期：22
• 页码：12075-12092
• 全文大小：836K
• 年卷期：v.51,no.22(November 19, 2012)
• ISSN：1520-510X

文摘

A series of modified, hafnium tert-butoxide ([Hf(OBup>tp>)₄]) compounds (1鈥?b>26) were crystallographically characterized, and representative species were then used to produce HfO₂nanoparticles. This systematically varied family of [Hf(OR)₄] compounds was developed from the reaction of [Hf(OBup>tp>)₄] with a series of (i) Lewis basic solvents, tetrahydrofuran, pyridine, or 1-methylimidazole; (ii) simple phenols, HOC₆H₄(R)-2 or HOC₆H₃(R)₂-2,6 where R = CH₃, CH(CH₃)₂, or C(CH₃)₃; and (iii) complex polydentate alcohols, tetrahydrofuran methanol (H-OTHF), pyridinecarbinol (H-OPy), and tris(hydroxymethylethane) (THME-H₃). The solvent-modified products were crystallographically characterized as [Hf(OBup>tp>)₄(solv)_n] (1鈥?b>3). The phenoxide (OAr)-exchanged [Hf(OBup>tp>)₄] products isolated from toluene were characterized as dimeric [Hf(OAr)_n(OBup>tp>)_4鈥?i>n]₂ (4 and 5) or [Hf(渭-OH)(OAr)₃(HOBup>tp>)]₂ (6 and 7) for the less sterically demanding OAr ligands and [Hf(OAr)_n(OBup>tp>)_4鈥?i>n(HOBup>tp>)] (8 and 9) monomers for the larger OAr ligands. When Lewis basic solvents were employed, solvated monomers of varied OAr substitutions were observed as [Hf(OAr)_n(OBup>tp>)_4鈥?i>n(solv)_x], where solv = THF (10, 11, and 13鈥?b>15) and py (16 and 19鈥?b>21). The nuclearities of the remaining complex polydentate alcohol derivatives ranged from monomers (24, OPy) to dimers (22, OTHF; 23, OPy) to tetramers (25 and 26, THME). On the basis of their nuclearities, select members of this family of [Hf(OR)₄] compounds (monomer, [Hf(OBup>tp>)₄], 8; dimer, 19a, 22; tetramer, 25) were used to determine the validity of using [Hf(OR)₄] precursors for the production of hafnia (HfO₂) nanoparticles under solvothermal (oleylamine/oleic acid) conditions. After a 650 掳C thermal treatment, the resulting powder X-ray diffraction pattern for each powder was found to be consistent with HfO₂ (PDF 00-040-1173), and after a 1000 掳C treatment, larger particles of HfO₂ (PDF 00-043-1017) were reported. Transmission electron microscopy images confirmed that nanomaterials had formed. Because identical processing conditions had been employed for each HfO₂ nanomaterial, the morphological variations observed in this study may be attributed to the individual precursors (鈥減recursor structure affect鈥?.