Nickel(II) fluoride
Encyclopedia
Nickel fluoride is the chemical compound
with the formula NiF2. Unlike many fluorides, NiF2 is stable in air. NiF2 comprises the passivating
surface that forms on nickel alloys, e.g. monel
, which is why such materials are good to store or transport hydrogen fluoride
or elemental fluorine
. Nickel is one of the few materials that can be used to store fluorine because it forms this coating. It is also used as a catalyst for the synthesis of chlorine pentafluoride
.
NiF2 is prepared by treatment of anhydrous nickel(II) chloride
with fluorine
at 350 °C:
The corresponding reaction of cobalt(II) chloride
results in oxidation of the cobalt
, whereas nickel remains in the +2 oxidation state
after fluorination because its +3 oxidation state is less stable. Chloride is more easily oxidized than nickel(II). This is a typical halogen displacement reaction, where a halogen plus a less active halide makes the less active halogen and the more active halide. Nickel(II) fluoride is also produced when fluorine reacts with nickel metal.
A melt of NiF2 and KF reacts to give the green compound K2[NiF4]. The structure of this material is closely related to some superconducting oxide materials.
Nickel(II) fluoride reacts with strong bases
to make nickel(II) hydroxide
, a green colored compound.
NiF2 + 2 NaOH → Ni(OH)2 + 2 NaF
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula NiF2. Unlike many fluorides, NiF2 is stable in air. NiF2 comprises the passivating
Passivation
Passivation is the process of making a material "passive", and thus less reactive with surrounding air, water, or other gases or liquids. The goal is to inhibit corrosion, whether for structural or cosmetic reasons. Passivation of metals is usually achieved by the deposition of a layer of oxide...
surface that forms on nickel alloys, e.g. monel
Monel
Monel is a trademark of Special Metals Corporation for a series of nickel alloys, primarily composed of nickel and copper, with some iron and other trace elements. Monel was created by David H. Browne, chief metallurgist for International Nickel Co...
, which is why such materials are good to store or transport hydrogen fluoride
Hydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
or elemental fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
. Nickel is one of the few materials that can be used to store fluorine because it forms this coating. It is also used as a catalyst for the synthesis of chlorine pentafluoride
Chlorine pentafluoride
Chlorine pentafluoride is an interhalogen compound with formula ClF5. It was first synthesized in 1963.Its square pyramidal structure with C4v symmetry was confirmed by its high resolution19F NMR spectrum.-Preparation:...
.
NiF2 is prepared by treatment of anhydrous nickel(II) chloride
Nickel(II) chloride
Nickel chloride , is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. It is very rarely found in nature as mineral nickelbischofite. A dihydrate is also known. In general nickel chloride, in various forms, is the most important source of...
with fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
at 350 °C:
- NiCl2Nickel(II) chlorideNickel chloride , is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. It is very rarely found in nature as mineral nickelbischofite. A dihydrate is also known. In general nickel chloride, in various forms, is the most important source of...
+ F2FluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
→ NiF2 + Cl2ChlorineChlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
The corresponding reaction of cobalt(II) chloride
Cobalt(II) chloride
Cobalt chloride is an inorganic compound of cobalt and chloride, with the formula CoCl2. It is usually supplied as the hexahydrate CoCl2·6H2O, which is one of the most commonly used cobalt compounds in the laboratory. The hexahydrate is deep purple in color, whereas the anhydrous form is sky blue...
results in oxidation of the cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
, whereas nickel remains in the +2 oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
after fluorination because its +3 oxidation state is less stable. Chloride is more easily oxidized than nickel(II). This is a typical halogen displacement reaction, where a halogen plus a less active halide makes the less active halogen and the more active halide. Nickel(II) fluoride is also produced when fluorine reacts with nickel metal.
A melt of NiF2 and KF reacts to give the green compound K2[NiF4]. The structure of this material is closely related to some superconducting oxide materials.
Nickel(II) fluoride reacts with strong bases
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
to make nickel(II) hydroxide
Nickel(II) hydroxide
Nickel hydroxide Ni2 is an insoluble compound commonly used in rechargeable battery electrodes. When charged these electrodes form nickel oxide-hydroxide. Nickel hydroxide is a precipitate formed when the hexaaquanickel ion is mixed with aqueous alkali...
, a green colored compound.
NiF2 + 2 NaOH → Ni(OH)2 + 2 NaF