Cobalt(II) nitrate

Cobalt(II) nitrate
Other names Cobaltous nitrate Nitric acid, cobalt(2+) salt
Identifiers
CAS number	10141-05-6 Y,  10026-22-9 (hexahydrate)
PubChem	25000
ChemSpider	23369 Y
UNII	65W79BFD5V Y
EC number	233-402-1
RTECS number	GG1109000
Jmol-3D images	Image 1
SMILES [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O
InChI InChI=1S/Co.2NO3/c;2*2-1(3)4/q+2;2*-1 Y Key: UFMZWBIQTDUYBN-UHFFFAOYSA-N Y InChI=1/Co.2NO3/c;2*2-1(3)4/q+2;2*-1 Key: UFMZWBIQTDUYBN-UHFFFAOYAS
Properties
Molecular formula	Co(NO3)2
Molar mass	182.943 g/mol (anhydrous) 291.03 g/mol (hexahydrate)
Appearance	pale red powder (anhydrous) red crystalline (hexahydrate)
Density	2.49 g/cm3 (anhydrous) 1.87 g/cm3 (hexahydrate)
Melting point	100 °C, decomp (anhydrous) 55 °C (hexahydrate)
Boiling point	100–105 °C, decomp (hexahydrate)
Solubility in water	134 g/100 ml, 0 °C (hexahydrate) soluble (anhydrous)
Solubility	soluble in alcohol, acetone (hexahydrate)
Structure
Coordination geometry	monoclinic (hexahydrate)
Hazards
MSDS	Cobalt (II) Nitrate MSDS
EU Index	027-009-00-2
EU classification	Carc. Cat. 2 Muta. Cat. 3 Repr. Cat. 2 Toxic (T) Dangerous for the environment (N)
R-phrases	R49, R60, R42/43, R68, R50/53
NFPA 704	0 2 0
Related compounds
Other anions	Cobalt(II) sulfate Cobalt(II) chloride Cobalt oxalate
Other cations	Iron(III) nitrate Nickel(II) nitrate
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Cobalt nitrate is the inorganic cobalt(II) salt of nitric acid, often with various amounts of water. It is more commonly found as a hexahydrate, Co(NO₃)₂·6H₂O, which is a red-brown deliquescent salt that is soluble in water and other polar solvents.

Composition and structures

As well as the anhydrous compound Co(NO₃)₂, there are several hydrates of cobalt(II) nitrate. The various degrees of hydration can be summarised by the general chemical formula Co(NO₃)₂·nH₂O, where n = 0, 2, 4, 6.

Anhydrous cobalt(II) nitrate adopts a three-dimensional polymeric network structure, with each cobalt(II) atom approximately octahedrally coordinated by six oxygen atoms, each from a different nitrate ion. Each nitrate ion coordinates to three cobalts.^[1] The dihydrate is a two-dimensional polymer, with nitrate bridges between Co(II) centres and hydrogen bonding holding the layers together. The tetrahydrate consists of discrete, octahedral [(H₂O)₄Co(NO₃)₂] molecules. The hexahydrate is better described as hexaaquacobalt(II) nitrate, [Co(OH₂)₆][NO₃]₂, as it consists of discrete [Co(OH₂)₆]²⁺ and [NO₃]⁻ ions.^[2]

Co(NO3)2	Co(NO3)2·2H2O	Co(NO3)2·4H2O	Co(NO3)2·6H2O

Uses

The high solubility of cobalt nitrate makes it a common source of cobalt in metal-organic frameworks and coordination chemistry. It is also reduced to metallic cobalt or precipitated on various substrates for Fischer-Tropsch catalysis.^[3]

Production

It is derived from reacting metallic cobalt or one of its oxides, hydroxides, or carbonate with nitric acid. It is commonly used in dyes and inks.^[4]

CoCO₃ + 2 HNO₃ + 5 H₂O → Co(NO₃)₂(H₂O)₆ + CO₂

Above 55 °C, it dehydrates to the trihydrate and at higher temperatures to the monohydrate.

References

1. ^ Tikhomirov, G. A.; Znamenkov, K. O.; Morozov, I. V.; Kemnitz, E.; Troyanov, S. I. (2002). "Anhydrous Nitrates and Nitrosonium Nitratometallates of Manganese and Cobalt, M(NO₃)₂, NO[Mn(NO₃)₃], and (NO)₂[Co(NO₃)₄]: Synthesis and Crystal Structure". Z. anorg. allg. Chem. 628 (1): 269–273. doi:10.1002/1521-3749(200201)628:1<269::AID-ZAAC269>3.0.CO;2-P. 
2. ^ Prelesnik, P. V.; Gabela, F.; Ribar, B.; Krstanovic, I. (1973). Cryst. Struct. Commun. 2: 581–583. 
3. ^ Ernst B, Libs S, Chaumette P, Kiennemann A. Appl. Catal. A 186 (1-2): 145-168 1999
4. ^ Lewis, Richard J., Sr. (2002). Hawley's Condensed Chemical Dictionary (14th Edition). John Wiley & Sons. http://www.knovel.com/knovel2/Toc.jsp?BookID=704&VerticalID=0