Reinecke's salt

Reinecke's salt is a chemical compound with the formula NH4[Cr(NCS)4(NH3)2]·H2O. The dark-red crystalline compound is soluble in boiling water, acetone, and ethanol.[2] The chromium atom is surrounded by six nitrogen atoms in an octahedral geometry. The NH3 ligands are mutually trans and the Cr–NCS groups are linear. The salt crystallizes with one molecule of water.[1]

Reinecke's salt
Names
IUPAC name
ammonium (OC-6-11)-diamminetetrakis(thiocyanato-N)chromate(1−)
Other names
ammonium tetrathiocyanato-
diamminechromate(III),

Reinecke salt,

ammonium reineckate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.625
EC Number
  • 237-003-3
UNII
Properties
C4H12N7OCrS4
Molar mass 354.42 g/mol
Appearance dark red solid
Density 1.49 g/cm3[1]
Melting point 270 °C (518 °F; 543 K)
Boiling point decomposes
soluble in hot water
Structure
octahedral
0 D
Hazards
Main hazards toxic
GHS pictograms
GHS Signal word Warning
H302, H312, H332, H400, H410
P261, P264, P270, P271, P273, P280, P301+312, P302+352, P304+312, P304+340, P312, P322, P330, P363, P391, P501
Related compounds
Related compounds
 [Co(NH3)6]Cl3,
KSCN,
Chromium(III) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure

It was first reported in 1863.[3] NH4[Cr(NCS)4(NH3)2] is prepared by treatment of molten NH4SCN (melting point around 145–150 °C) with (NH4)2Cr2O7.[4]

Use

This salt was once widely used to precipitate primary and secondary amines as their ammonium salts. Included in the amines that effectively form crystalline precipitates are those derived from the amino acids, including proline and hydroxyproline. It also reacts with Hg2+ compounds, giving a red color or a red precipitate.

References
  1. Saito, Y.; Takeuchi, Y.; Pepinsky, R. (1955). "The Crystal Structure of Ammonium Reineckate". Zeitschrift für Kristallographie, Kristallgeometrie, Kristallphysik, Kristallchemie. 106 (1–6): 476–477. doi:10.1524/zkri.1954.106.16.476. S2CID 101134761.
  2. Peppel, T.; Schmidt, C.; Köckerling, M. (2011). "Synthesis, Properties, and Structures of Salts with the Reineckate Anion, [CrIII(NCS)4(NH3)2]−, and Large Organic Cations". Zeitschrift für Anorganische und Allgemeine Chemie. 637 (10): 1314–1321. doi:10.1002/zaac.201100091.
  3. Reinecke, A. (1863). "Über Rhodanchromammonium-Verbindungen". Annalen der Chemie und Pharmacie. 126: 113–118. doi:10.1002/jlac.18631260116.
  4. Dakin, H. D. (1943). "Reinecke Salt". Organic Syntheses. 2: 555.
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