Reinecke's salt

Reinecke's salt

Names
IUPAC names Chromate(1−), diaminetetrakis- (thiocyanato-N)-, ammonium, (OC-6-11)-
Other names ammonium tetrathiocyanato- diamminechromate(III), Reinecke salt, ammonium reineckate
Identifiers
CAS Number	13573-16-5
ChemSpider	21106473
Jmol 3D model	Interactive image
RTECS number	na
InChI InChI=1S/4CNS.Cr.3H3N.H2O/c4*2-1-3;;;;;/h;;;;;3*1H3;1H2/q4*-1;+3;;;;/p+1 Key: GXUDINOISGOIAV-UHFFFAOYSA-O InChI=1/4CNS.Cr.3H3N.H2O/c4*2-1-3;;;;;/h;;;;;3*1H3;1H2/q4*-1;+3;;;;/p+1/rC4H6CrN6S4.H3N.H2O/c6-5(7,8-1-12,9-2-13,10-3-14)11-4-15;;/h6-7H3;1H3;1H2/q-1;;/p+1 Key: GXUDINOISGOIAV-JJHXSEQHAU
SMILES [NH4+].S=C=N/[Cr-3]([NH3+])([NH3+])(/N=C=S)(/N=C=S)/N=C=S.O
Properties
Chemical formula	C4H13.33N7O0.66CrS4
Molar mass	354.42 g/mol
Appearance	dark red solid
Density	1.49 g/cm^3[1]
Melting point	270 °C (518 °F; 543 K)
Boiling point	decomposes
Solubility in water	soluble in hot water
Structure
Coordination geometry	octahedral
Dipole moment	0 D
Hazards
Main hazards	toxic
R-phrases	20/21/22
S-phrases	36
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

Reinecke's salt is a chemical compound with the formula NH₄[Cr(NCS)₄(NH₃)₂]·²⁄₃H₂O. 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]

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: 476–477. doi:10.1524/zkri.1954.106.16.476.
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: 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". Org. Synth. 2: 555.