Cobalt(II) cyanide

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Cobalt(II) cyanide
Names
IUPAC name
Cobalt(II) cyanide
Other names
cobaltous cyanide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.008.028 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/2CN.Co/c2*1-2;/q2*-1;+2 Yes check.svgY
    Key: CWZOMTYLSNXUEL-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/2CN.Co/c2*1-2;/q2*-1;+2
    Key: CWZOMTYLSNXUEL-UHFFFAOYAR
  • [Co+2].[C-]#N.[C-]#N
Properties
Co(CN)2
Molar mass 110.968 g/mol
Appearancedeep-blue powder
hygroscopic
Density 1.872 g/cm3 (anhydrous)
Melting point 220 °C (428 °F; 493 K) (decomposes)
insoluble [1]
Solubility dihydrate
degraded with dissolution by NaCN, KCN, NH4OH, HCl
+3825·10−6 cm3/mol
Related compounds
Other anions
Cadmium chloride,
Cadmium iodide
Other cations
Zinc cyanide,
Calcium cyanide,
Magnesium cyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cobalt(II) cyanide is the inorganic compound with the empirical formula Co(CN)2 and structural formula Co3[Co(CN)5]2. It is a coordination polymer that has attracted intermittent attention over many years in the areas of inorganic synthesis and homogeneous catalysis. [2] The anhydrous and octahydrate forms are both blue solids insoluble in water.

Contents

Preparation and structure

The octahydrate is prepared by the reaction between tetraethylammonium pentacyanocobaltate and cobalt(II) chloride: [3]

2 (Et4N)3[Co(CN)5] + 3 Co(H2O)6Cl2 → [Co(H2O)6]3[Co(CN)5]2 · 2H2O↓ + 6 Et4N+ + 6 Cl−

Heating of the octahydrate at 100 °C produces the anhydrous form. [3] The anhydrous form can also be prepared from the reaction of cobalt(II) bromide and potassium cyanide or sodium cyanide in liquid ammonia, then heating the resulting ammoniate to 210 °C in ethyl benzoate. [4]

The structural formula Co3[Co(CN)5]2 shows that cobalt(II) cyanide consists of Co2+ and [Co(CN)5]3– (pentacyanocobaltate) ions. [3]

Oxygenation and redox

A red trihydrated has also been reported, [5] but this was later shown to be the oxygenated derivative containing the ion [Co(CN)5(O2)]3–. [6] [7] [8]

The oxygenated derivative is obtained as a reddish-brown precipitate by adding two equivalents of potassium cyanide to a solution of cobalt(II) salts in air. [9] With excess cyanide, the red-brown solid dissolves to give pentacyanocobaltate, which oxidizes in the presence of oxygen to hexacyanocobaltate(III). [2] [8]

Uses

Cobalt(II) cyanide has been used as a precursor to dicobalt octacarbonyl. [10]

References

  1. ↑ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, Florida: CRC Press. ISBN   0-8493-0487-3.
  2. 1 2 Kwiatek, Jack (1968). "Reactions Catalyzed by Pentacyanocobaltate(II)". Catalysis Reviews. 1: 37–72. doi:10.1080/01614946808064700.
  3. 1 2 3 Beauvais, Laurance G.; Long, Jeffrey R. (2002-10-01). "Co 3 [Co(CN) 5 ] 2 : A Microporous Magnet with an Ordering Temperature of 38 K". Journal of the American Chemical Society. 124 (41): 12096–12097. doi:10.1021/ja027768z. ISSN   0002-7863 . Retrieved 2025-06-22.
  4. ↑ Mosha, D. M. S. J. Chem. Soc. Pak. 1985, 7, 173.
  5. ↑ Weiss, Armin; Rothenstein, W. (1963). "Cobalt(II) Cyanide, its Three-Demensional Frame-work Structure and Zeolitic Compounds". Angewandte Chemie International Edition. 2 (7): 396. doi:10.1002/anie.196303962.
  6. ↑ Brown, Leo D.; Raymond, Kenneth N. (1975-11-01). ".sigma.-Bonded dioxygen adduct of the pentacyanocobaltate(II) anion. Crystal structure of tris(tetraethylammonium)dioxopentacyanocobaltate(II) pentahydrate". Inorganic Chemistry. 14 (11): 2595–2601. doi:10.1021/ic50153a003. ISSN   0020-1669 . Retrieved 2025-06-22.
  7. ↑ White, D. A.; Solodar, A. J.; Baizer, M. M. (1972). "Tetraalkylammonium pentacyanocobaltates. Their preparation, properties, and reactivity". Inorganic Chemistry. 11 (9): 2160–2167. doi:10.1021/ic50115a034. ISSN   0020-1669 . Retrieved 2025-06-22.
  8. 1 2 Poskozim, Paul S. (1969). "The preparation of potassium hexacyanocobaltate(III)". Journal of Chemical Education. 46 (6): 384. doi:10.1021/ed046p384. ISSN   0021-9584 . Retrieved 2025-06-22.
  9. ↑ Bigelow, John H.; Bailar Jr., John C. (1946). "Potassium Hexacyanocobaltate(III)". Inorganic Syntheses. Inorganic Syntheses. Vol. 2. pp. 225–227. doi:10.1002/9780470132333.ch72. ISBN   9780470132333.{{cite book}}: ISBN / Date incompatibility (help)
  10. ↑ Sternberg, Heinz W.; Wender, Irving; Orchin, Milton; Lynch Jr., M. A.; Sesny, W. J. (1957). "Cobalt Tetracarbonyl Hydride". Inorganic Syntheses. Inorganic Syntheses. Vol. 5. pp. 192–195. doi:10.1002/9780470132364.ch55. ISBN   9780470132364.{{cite book}}: ISBN / Date incompatibility (help)


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