コバルト(III)トリフルオリド

解説

フッ化コバルト(Ⅲ)：CoF3(115.93)．三フッ化コバルトともいう．フッ化コバルト(Ⅱ)にフッ素を作用させると得られる．淡褐色の粉末．密度3.88 g cm－3．封管中で安定である．湿った空気とただちに反応して黒褐色の粉末になる．熱すると分解する．水と反応して水酸化コバルト(Ⅲ)を生じる．炭化水素のフッ素化剤として用いられる．毒性が強く組織をはげしく刺激する．

化学的特性

The heat of formation is —187 kcal mole-1 and the magnetic moment is 1-60 B.M. at 90°K rising to 2.46 B.M. at 293°K; it is thus a high spin compound but not magnetically dilute.
Anhydrous cobalt(III) fluoride turns dark in the presence of traces of water and reacts violently with the liquid-evolving oxygen. When heated in an inert atmosphere above 350°, cobalt(II) fluoride is formed. It reacts vigorously with many elements, e.g. Al, P, As, S, I, being reduced to cobalt(II) fluoride. It is insoluble in alcohol, ether and benzene and is a useful fluorinating agent in organic chemistry.

物理的性質

Light brown hexagonal crystal; density 3.88 g/cm³; moisture sensitive; stable in dry air; melts at 927°C; reacts with water.

使用

Cobalt(III) fluoride is a powerful fluorinating agent.

製造方法

Cobalt(III) fluoride may be prepared by reaction of elemental fluorine with cobalt(II) fluoride, cobalt(II) chloride or cobalt(III) oxide at 300 to 400°C.
2CoF₂ + F₂ → 2CoF₃
2CoCl₂ + 3F₂ → 2CoF₃ + 2Cl₂
It should be stored in a sealed glass ampule, free from moisture.
Electrolytic oxidation of cobalt(II) fluoride in 40% hydrofluoric acid yields hydrated cobalt(III) fluoride, CoF₃·3.5H₂O (3.5 is the stoichiometric amount of water per CoF3 molecule in the crystal lattice).

危険性

Strong irritant to tissue.

参考文献

M.A. Hepworth, et al., Acta Crystallogr., 10, 63 (1957), DOI: 10.1107/S0365110X57000158.