Copper(I) thiocyanate

Copper(I) thiocyanate

Copper(I) thiocyanate
Names
Other names
Cuprous thiocyanate
Identifiers
1111-67-7
ChemSpider 55204
PubChem 24857968
Properties
CuSCN
Molar mass 121.628 g/mol[1]
Appearance white powder
Density 2.88 g/cm3[2]
Melting point 1,084[1] °C (1,983 °F; 1,357 K)
8.427·10−7 g/L (20 °C)
Related compounds
Other anions
 Copper(I) iodide, copper(I) cyanide
Other cations
 Ammonium thiocyanate
Potassium thiocyanate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Copper(I) thiocyanate (or cuprous thiocyanate) is a coordination polymer with formula CuSCN. It is an air-stable, white solid used as a precursor for the preparation of other thiocyanate salts .

Structure

Two polymorphs have been characterized. The one pictured above features copper(I) in a characteristic tetrahedral coordination geometry. The sulfur end of the SCN- ligand is triply bridging.[2]

Synthesis

Copper(I) thiocyanate forms from the spontaneous decomposition of dry black copper(II) thiocyanate, releasing thiocyanogen, especially when heated. It is also formed from copper(II) thiocyanate under water, releasing (among others) thiocyanic acid and the highly poisonous hydrogen cyanide.[3]
It is conveniently prepared from solutions of copper(II) in water, such as copper(II) sulphate. To a copper(II) solution sulphurous acid is added and then a soluble thiocyanate is added (preferably slowly, while stirring[4]). Copper(I) thiocyanate is precipitated as a white powder.[5] Alternatively, a thiosulfate solution may be used as a reducing agent.

Double salts

Copper(I) thiocyanate forms one double salt with the group 1 elements, CsCu(SCN)2. The double salt only forms from concentrated solutions of CsSCN, into which CuSCN dissolves. From less concentrated solutions, solid CuSCN separates reflecting its low solubility.[6] When brought together with potassium, sodium or barium thiocyanate, and brought to crystallisation by concentrating the solution, mixed salts will crystallise out. These are not considered true double salts. As with CsCu(SNC)2, copper(I) thiocyanate separates out when these mixed salts are redissolved or their solutions diluted.[7]

Uses

Copper(I) thiocyanate is a hole conductor, a semiconductor with a wide band gap (3.6 eV, therefore transparent to visible and near infrared light).[8] It is used in photovoltaics in some third-generation cells as a hole transfer layer. It acts as a P-type semiconductor and as a solid-state electrolyte. It is often used in dye-sensitized solar cells. Its hole conductivity is however relatively poor (0.01 S.m-1. This can be improved by various treatments, e.g. exposure to gaseous chlorine or doping with (SCN)2.[9]


CuSCN with NiO act synergically as a smoke suppressant additive in PVC.

CuSCN precipitated on carbon support can be used for conversion of aryl halides to aryl thiocyanates.[10]

References

  1. 1 2 "Properties of Copper(I) thiocyanate". Chemspider. Alfa Aesar 40220. Retrieved 5 January 2016.
  2. 1 2 Smith, D. L.; Saunders, V. I. "Preparation and Structure Refinement of the 2H Polytype of beta-Copper(I) Thiocyanate" Acta Crystallographica B, 1982, volume 38, 907-909. doi:10.1107/S0567740882004361
  3. ↑ David Tudela (1993). "The Reaction of Copper(II) with Thiocyanate Ions (Letter to the Editor)". Journal of Chemical Education. 70 (2): 174. doi:10.1021/ed070p174.3.PDF copy
  4. ↑ Matthew Dick (1969). "Use of cuprous thiocyanate as a short-term continuous marker for faeces". Gut. 10: 408–412 (408). doi:10.1136/gut.10.5.408.PDF copy
  5. ↑ Reece H. Vallance, Douglas F. Twiss and Miss Annie R. Russell (1931). J. Newton Friend, ed. A text-book of inorganic chemistry, volume VII, part II. Charles Griffin & Company Ltd. p. 282.
  6. ↑ H.L.Wells (1902). "On some double and triple thiocyanates". American Chemical Journal. 28: 245–284 (263).
  7. ↑ Herbert E. Williams (1915). The chemistry of cyanogen compounds. J. & A. Churchill, London. pp. 202–203.
  8. ↑ https://books.google.com/books?id=1qnL0qO9KNcC&pg=PA256&dq=CuSCN&hl=en&sa=X&redir_esc=y#v=onepage&q=CuSCN&f=false
  9. ↑ https://books.google.com/books?id=NJJTW_zU5QUC&pg=PA164&dq=CuSCN&hl=en&sa=X&redir_esc=y#v=onepage&q=CuSCN&f=false
  10. ↑ https://books.google.com/books?id=V7ahxSHqMqMC&pg=PA121&dq=CuSCN&hl=en&sa=X&redir_esc=y#v=onepage&q=CuSCN&f=false
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