Cobalt(II) cyanate

Cobalt(II) cyanate is the hypothetical inorganic compound with the formula Co(OCN)₂.

Cobalt(II) cyanate

Identifiers
CAS Number	38150-63-9 Y
3D model (JSmol)	Interactive image isocyanate: Interactive image
PubChem CID	isocyanate: 15345298
InChI isocyanate: InChI=1S/2CNO.Co/c2*2-1-3;/q2*-1;+2 Key: JXDJYNWFLIUUIU-UHFFFAOYSA-N
SMILES C(#N)[O-].C(#N)[O-].[Co+2] isocyanate: C(=[N-])=O.C(=[N-])=O.[Co+2]
Properties
Chemical formula	Co(OCN)2
Molar mass	142.97 g/mol
Related compounds
Other anions	Cobalt(II) thiocyanate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The simple cobalt(II) cyanate has not been proven to be made. However, the tetraisocyanatocobalt(II) ion (Co(NCO)₄^2-) is known and its blue color and is used as a qualitative test for cobalt(II) ions.

History

Cobalt(II) cyanate was claimed to have been produced in 1952 by carefully heating pyridine cobalt(II) cyanate under vacuum. The nature of the compound produced has not been elucidated by X-ray diffraction.^[1]

In contrast, the tetraisocyanatocobalt(II) ion (Co(NCO)₄^2-) has been identified by X-ray crystallography and is widely known.^[2] After being first produced in 1871, it has been used as a qualitative test for cobalt(II).^[3]

Other cyanate complexes of cobalt have been discovered, such as tetrakis(pyridine)cobalt(II) cyanate.^[4]

Complexes

Tetracyanatocobaltate(II)

A solution of tetracyanatocobaltate(II)

Multiple compounds of the related tetracyanatocobaltate(II) has been structurally elucidated, such as [Co(C₅H₅)₂]₂[Co(NCO)₄]. All of these complexes have an intense blue color.^[2][5]

Potassium tetraisocyanatocobaltate(II) has been produced by the reaction of potassium cyanate and cobalt(II) nitrate:^[6]

4 KOCN + Co(NO₃)₂ → K₂[Co(NCO)₄] + 2 KNO₃

Tetracyanatocobaltate(II) salts with other counterions, such as cobaltcenium [Co(C₅H₅)]⁺ and EMIM are known.^[2]

Other adducts

Cobalt(II) cyanate complexes have been produced by the addition of potassium cyanate to a soluble cobalt salt, such as cobalt(II) chloride, followed by the addition of the complexing agent, such as pyridine, bipyridine,^[7] quinoline, and 2,6-dimethylpyrazine.^[8]

Structure

Although the simple cyanate is unknown, the structure of the tetracyanatocobaltate(II) ion has been elucidated. The [Co(NCO)₄]^2- ion consists of a nitrogen-bonded tetrahederal central cobalt atom. The cobalt-nitrogen bond length is about 1.96 Å.^[2]