四氢硼酸钍Th(BH4)4醚加合物的合成与表征及硼化钍薄膜的化学气相沉积,Inorganic Chemistry

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四氢硼酸钍Th(BH4)4醚加合物的合成与表征及硼化钍薄膜的化学气相沉积
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2023-02-27 , DOI: 10.1021/acs.inorgchem.2c03960
Andrew C Dunbar ₁ , John E Gozum ₁ , Wenbin Lin ₁ , Vincent J Flores ₁ , Gregory S Girolami ₁

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在各种醚类溶剂中用 LiBH ₄处理 ThCl ₄得到加合物 Th(BH ₄ ) ₄ (Et ₂ O) ₂、Th(BH ₄ ) ₄ (thf) ₂和 Th(BH ₄ ) ₄ (dme) (thf =四氢呋喃和 dme = 1,2-二甲氧基乙烷）。这三种化合物的结构已通过单晶 X 射线衍射确定：如果认为四氢硼酸基团占据一个配位点，则 Et 2 _O和 thf 配合物采用反八面体配位几何结构，而 dme 配合物则显示出顺式-八面体结构。每种化合物中的所有四个 BH ₄^-配体都是三齿的，使每个钍中心都处于 14 坐标。Th···B 距离范围为 2.64 到 2.67 Å，Th-O 键长为 2.47-2.52 Å。我们提出 Th(BH ₄ ) ₄ (thf) ₂的晶体与 U(BH ₄ ) ₄ (thf) ₂的晶体是同晶的，但由于伪对称性，后者被报道在一个太小的晶胞中2. IR 光谱和¹ H 和¹¹ B NMR 数据也有报道。所有三种加合物都是挥发性的，在 60 °C 和 10 ^{–4时容易升华}Torr，使它们有可能用作硼化钍薄膜化学气相沉积 (CVD) 的前体。Th(BH ₄ ) ₄ (Et ₂ O) ₂在加热到 350 °C 的玻璃、Si(100) 和铝基板上的通过产生近似化学计量的 ThB ₂的非晶薄膜；由Th(BH ₄ ) ₄ (thf) ₂沉积的薄膜具有更接近ThB _{2.5 的}化学计量并且包含一些氧。报告了这些薄膜的俄歇、XPS、XRD 和 SEM 研究。

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Synthesis and Characterization of Ether Adducts of Thorium Tetrahydroborate Th(BH4)4 and Chemical Vapor Deposition of Thorium Boride Thin Films

Treating ThCl₄ with LiBH₄ in various ethereal solvents affords the adducts Th(BH₄)₄(Et₂O)₂, Th(BH₄)₄(thf)₂, and Th(BH₄)₄(dme) (thf = tetrahydrofuran and dme = 1,2-dimethoxyethane). The structures of these three compounds have been established by single-crystal X-ray diffraction: if the tetrahydroborate groups are considered as occupying one coordination site, the Et₂O and thf complexes adopt trans-octahedral coordination geometries, whereas the dme complex exhibits a cis-octahedral structure. All four BH₄^– ligands in each compound are tridentate, rendering each thorium center 14-coordinate. The Th···B distances range from 2.64 to 2.67 Å, and the Th–O bond lengths are 2.47–2.52 Å. We propose that crystals of Th(BH₄)₄(thf)₂ are isomorphous with those of U(BH₄)₄(thf)₂, but owing to pseudosymmetry the latter was reported in a unit cell that was too small by a factor of 2. IR spectra and ¹H and ¹¹B NMR data are reported as well. All three adducts are volatile, subliming readily at 60 °C and 10^–4 Torr, making them potentially useful as precursors for the chemical vapor deposition (CVD) of thin films of thorium boride. Passage of Th(BH₄)₄(Et₂O)₂ over glass, Si(100), and aluminum substrates heated to 350 °C yields amorphous films of approximate stoichiometry ThB₂; films deposited from Th(BH₄)₄(thf)₂ have stoichiometries closer to ThB_2.5 and contain some oxygen. Auger, XPS, XRD, and SEM studies of these films are reported.

更新日期：2023-02-27

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