每周分子 | Molecule of the Week

Original ACS 美国化学会 ACS美国化学会 2022-07-01

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每周分子：四氟铍酸铵

Molecule of the Week:

Ammonium tetrafluoroberyllate

四氟铍酸铵是含有四氟铍酸阴离子的几种盐之一，其中的四个氟原子以正四面体排列方式与一个铍原子共价键结合。四氟铍酸阴离子还被用于制备碱金属盐、碱土金属盐、过渡金属盐和许多有机胺盐，其中一些盐具有不同强度的水合作用。

四氟铍酸铵也被称为氟化铍铵。在氟化氢铵 [(NH ₄)HF₂]的水溶液中溶解氢氧化铍 [Be(OH)₂]来制备四氟铍酸铵。将该水溶液在蒸发结晶器中浓缩可形成四氟铍酸铵盐晶体。四氟铍酸铵盐晶体为正交晶系(如图所示)，密度为1.71g/mL。像所有含铍化合物一样，它具有极强的毒性。

将四氟铍酸铵加热至≈1000°C来生产氟化铍(BeF₂)玻璃。继而在1300°C下用镁还原BeF₂来制造金属铍。在过去的几年里，铍一直供不应求；2016 年，俄罗斯托木斯克理工大学的L. N. Malyutin及其同事们改进了制备金属过程中纯化四氟铍酸铵的方法。

先进材料制造商(如Materialon)使用四氟铍酸铵生产含铍产品。Materion使用上述合成路线来制备BeF₂和金属铍。

除了作为制备金属的前体之外，BeF₂在核能工业中也有所应用。由四氟铍酸铵生产的铍金属已被用于制造詹姆斯·韦伯太空望远镜的反射镜，该太空望远镜计划于今年晚些时候被发射入太空。

四氟铍酸信息速览

CAS 登记号	14874-86-3
SciFinder命名	Beryllate(2–), tetrafluoro-, ammonium (1:2)
分子式	H₈BeF₄N₂
摩尔质量	121.08 g/mol
外观	白色晶体
熔点	280 °C (dec.)
水溶性	323 g/L

四氟铍酸危害信息

GHS*分类：急性毒性，口服，分类3
H301-吞食有毒
GHS分类：皮肤腐蚀/刺激，分类2
H315-引起皮肤刺激
GHS分类：致敏，皮肤，分类1B
H317-可能引起皮肤过敏反应
GHS分类：严重眼损伤/眼刺激，分类2A
H319-引起严重的眼刺激
GHS分类：急性毒性，吸入，分类1
H330-吸入致命
GHS分类：特定目标器官毒性，单次接触，呼吸道刺激，分类3
H335-可能引起呼吸道刺激
GHS分类：致癌性，分类1A
H350-吸入可能致癌
GHS分类：特定目标器官毒性，反复接触，分类1
H372-长期或反复接触导致器官损伤
GHS分类：对水生环境有害，长期危害
H411-有水生生物毒性并具有长期影响

【关于每周分子】

自2001年以来，“每周分子”已成为广受欢迎的栏目。多数分子由读者推荐。每个结构都经由科学家审查，并以3-D和平面图像的形式显示，同时附有该分子简介。可以通过美国化学文摘社 (CAS) 提供的CAS SciFinderⁿ中的CAS REGISTRY获取“每周分子”的更多信息。CAS REGISTRY中的每条物质信息都展示了物质的CAS登记号、索引名、通用名、商品名、书目信息等其他更多信息。发送邮件至motw@acs.org推荐您感兴趣的分子吧。

Diammonium tetrafluoroberyllate is one of several salts of the tetrafluoroberyllate anion, in which four fluorine atoms are covalently bonded to a beryllium atom in a tetrahedral arrangement. The anion has also been prepared as salts of alkali metals, alkaline earths, transition metals, and many organic amines, some with varying degrees of hydration.

Also called ammonium beryllium fluoride, the salt is formed by dissolving beryllium hydroxide [Be(OH)₂] in an aqueous solution of ammonium hydrogen fluoride [(NH₄)HF₂]. The aqueous solution is concentrated in an evaporative crystallizer to form the diammonium tetrafluoroberyllate salt. Its crystals are orthorhombic (shown) with a density of 1.71 g/mL. Like all beryllium-containing compounds, it is extremely toxic.

Diammonium tetrafluoroberyllate is used to produce beryllium fluoride (BeF₂) glass by heating the salt to ≈1000 °C. BeF2, in turn, can be used to make beryllium metal by reducing it with elemental magnesium at 1300°C. In the past several years, beryllium has been in short supply; in 2016, L. N. Malyutin and co-workers at Tomsk Polytechnic University (Russia) developed improved methods to purify diammonium tetrafluoroberyllate on its way to making the metal.

Advanced materials manufacturers, such as Materion (Mayfield Heights, OH), use ammonium tetrafluoroberyllate to make their beryllium-containing products. Materion uses the synthetic route described above to make BeF₂ and the metal.

In addition to being the precursor to the metal, BeF₂ has applications in the nuclear energy industry. Beryllium metal produced from ammonium tetrafluoroberyllate was used to make the mirrors of the James Webb Space Telescope, which is scheduled to be launched later this year.

Ammonium tetrafluoroberyllatefast facts

CAS Reg. No.	14874-86-3
SciFinder nomenclature	Beryllate(2–), tetrafluoro-, ammonium (1:2)
Empirical formula	H₈BeF₄N₂
Molar mass	121.08 g/mol
Appearance	White crystals
Melting point	280 °C (dec.)
Water solubility	323 g/L

Ammonium tetrafluoroberyllate hazard information

Acute toxicity, oral, category 3
H301-Toxic if swallowed
Skin corrosion/irritation, category 2
H315-Causes skin irritation
Sensitization, skin, category 1
H317-May cause an allergic skin reaction
Serious eye damage/eye irritation, category 2A
H319-Causes serious eye irritation
Acute toxicity, inhalation, category 1
H330-Fatal if inhaled
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3
H335-May cause respiratory irritation
Carcinogenicity, category 1A
H350-May cause cancer by inhalation
Specific target organ toxicity, repeated exposure, category 1A
H372-Causes damage to organs through prolonged or repeated exposure
Hazardous to the aquatic environment, long-term hazard
H411-Toxic to aquatic life with long-lasting effects

About Molecule of the Week

MOTW has been a popular feature on ACS website since 2001. Many molecules are suggested by our website visitors. Every structure is reviewed by a scientist and displayed in 3-D and flat images with a brief description. Each week’s molecule also links to a sample record from the CAS REGISTRY, which is searched using CAS SciFinderⁿ. Each record displays the registry number, index name and synonyms, bibliographic information, and more. Send us a molecule suggestion at motw@acs.org.

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