Chromium(III) chloride (also called chromic chloride) describes any of several chemical compounds with the formula CrCl3 · xH2O, where x can be 0, 5, and 6. The anhydrous compound with the formula CrCl3 is a violet solid. The most common form of the trichloride is the dark green hexahydrate, CrCl3 · 6 H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.
Anhydrous chromium(III) chloride adopts the YCl3 structure, with Cr3+ occupying one third of the octahedral interstices in alternating layers of a pseudo-cubic close packed lattice of Cl− ions. The absence of cations in alternate layers leads to weak bonding between adjacent layers. For this reason, crystals of CrCl3cleave easily along the planes between layers, which results in the flaky (micaceous) appearance of samples of chromium(III) chloride.[6][7] If pressurized to 9.9 GPa it goes under a phase transition.[8]
Space-filling model of cubic close packing of chloride ions in the crystal structure of CrCl3
The hydrated chromium(III) chlorides display the somewhat unusual property of existing in a number of distinct chemical forms (isomers), which differ in terms of the number of chloride anions that are coordinated to Cr(III) and the water of crystallization. The different forms exist both as solids and in aqueous solutions. Several members are known of the series of [CrCl3−z(H2O)n]z+. The common hexahydrate can be more precisely described as [CrCl2(H2O)4]Cl · 2 H2O. It consists of the cation trans-[CrCl2(H2O)4]+ and additional molecules of water and a chloride anion in the lattice.[9] Two other hydrates are known, pale green [CrCl(H2O)5]Cl2 · H2O and violet [Cr(H2O)6]Cl3. Similar isomerism is seen with other chromium(III) compounds.
The hydrated chlorides are prepared by treatment of chromate with hydrochloric acid and aqueous methanol.
Reactions
Slow reaction rates are common with chromium(III) complexes. The low reactivity of the d3 Cr3+ ion can be explained using crystal field theory. One way of opening CrCl3 up to substitution in solution is to reduce even a trace amount to CrCl2, for example using zinc in hydrochloric acid. This chromium(II) compound undergoes substitution easily, and it can exchange electrons with CrCl3 via a chloride bridge, allowing all of the CrCl3 to react quickly.
With the presence of some chromium(II), however, solid CrCl3 dissolves rapidly in water. Similarly, ligand substitution reactions of solutions of [CrCl2(H2O)4]+ are accelerated by chromium(II) catalysts.
With molten alkali metalchlorides such as potassium chloride, CrCl3 gives salts of the type M3CrCl6 and K3Cr2Cl9, which is also octahedral but where the two chromiums are linked via three chloride bridges.
Chromium(III) chloride has also been used as a Lewis acid in organic reactions, for example to catalyse the nitroso Diels-Alder reaction.[16]
Dyestuffs
A number of chromium-containing dyes are used commercially for wool. Typical dyes are triarylmethanes consisting of ortho-hydroxylbenzoic acid derivatives.[17]
Precautions
Although trivalent chromium is far less poisonous than hexavalent, chromium salts are generally considered toxic.
^A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
^Meiling Hong (2022). "Pressure-Induced Structural Phase Transition and Metallization of CrCl3 under Different Hydrostatic Environments up to 50.0 GPa". Inorg. Chem. 61 (12): 4852–4864. doi:10.1021/acs.inorgchem.1c03486. PMID 35289613. S2CID 247452267.
^Ian G. Dance, Hans C. Freeman "The Crystal Structure of Dichlorotetraaquochromium(III) Chloride Dihydrate: Primary and Secondary Metal Ion Hydration" Inorganic Chemistry 1965, volume 4, 1555–1561. doi:10.1021/ic50033a006
^Brauer, Georg (1965) [1962]. Handbuch Der Präparativen Anorganischen Chemie [Handbook of Preparative Inorganic Chemistry] (in German). Vol. 2. Stuttgart; New York, New York: Ferdinand Enke Verlag; Academic Press, Inc. p. 1340. ISBN978-0-32316129-9. Retrieved 2014-01-10.
^Pray, A. P. (1990). "Anhydrous Metal Chlorides". Inorganic Syntheses. Inorganic Syntheses. Vol. 28. p. 321–2. doi:10.1002/9780470132401.ch36. ISBN9780470132401.
^Philip Boudjouk, Jeung-Ho So (1992). "Solvated and Unsolvated Anhydrous Metal Chlorides from Metal Chloride Hydrates". Inorganic Syntheses. Inorganic Syntheses. Vol. 29. pp. 108–111. doi:10.1002/9780470132609.ch26. ISBN9780470132609.{{cite book}}: CS1 maint: uses authors parameter (link)
^John T. Dixon, Mike J. Green, Fiona M. Hess, David H. Morgan "Advances in selective ethylene trimerisation – a critical overview" Journal of Organometallic Chemistry 2004, Volume 689, pp 3641-3668. doi:10.1016/j.jorganchem.2004.06.008
^Feng Zheng, Akella Sivaramakrishna, John R. Moss "Thermal studies on metallacycloalkanes" Coordination Chemistry Reviews 2007, Volume 251, 2056-2071. doi:10.1016/j.ccr.2007.04.008
^Calvet, G.; Dussaussois, M.; Blanchard, N.; Kouklovsky, C. (2004). "Lewis Acid-Promoted Hetero Diels-Alder Cycloaddition of α-Acetoxynitroso Dienophiles". Organic Letters. 6 (14): 2449–2451. doi:10.1021/ol0491336. PMID 15228301.
Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
The Merck Index, 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.
J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
K. Takai, in Handbook of Reagents for Organic Synthesis, Volume 1: Reagents, Auxiliaries and Catalysts for C-C Bond Formation, (R. M. Coates, S. E. Denmark, eds.), pp. 206–211, Wiley, New York, 1999.
External links
Wikimedia Commons has media related to Chromium(III) chloride.
International Chemical Safety Card 1316 (anhydr. CrCl3)
International Chemical Safety Card 1532 (CrCl3·6H2O)
NIOSH Pocket Guide to Chemical Hazards
April 16, 2023
chromium, chloride, also, called, chromic, chloride, describes, several, chemical, compounds, with, formula, crcl3, where, anhydrous, compound, with, formula, crcl3, violet, solid, most, common, form, trichloride, dark, green, hexahydrate, crcl3, chromium, chl. Chromium III chloride also called chromic chloride describes any of several chemical compounds with the formula CrCl3 x H2O where x can be 0 5 and 6 The anhydrous compound with the formula CrCl3 is a violet solid The most common form of the trichloride is the dark green hexahydrate CrCl3 6 H2O Chromium chlorides find use as catalysts and as precursors to dyes for wool Chromium III chloride AnhydrousHexahydrateNamesIUPAC names Chromium III chlorideChromium trichlorideOther names Chromic chlorideIdentifiersCAS Number 10025 73 7 Y10060 12 5 hexahydrate Y3D model JSmol Interactive imageChEBI CHEBI 53351 YChEMBL ChEMBL1200528 NChemSpider 4954736 YDrugBank DB09129ECHA InfoCard 100 030 023Gmelin Reference 1890 130477 532690PubChem CID 6452300RTECS number GB5425000UNII Z310X5O5RP YKB1PCR9DMW hexahydrate YCompTox Dashboard EPA DTXSID20858722InChI InChI 1S 3ClH Cr h3 1H q 3 p 3 YKey QSWDMMVNRMROPK UHFFFAOYSA K YInChI 1 3ClH Cr h3 1H q 2 p 3Key HUQISNLCWMVGCG DFZHHIFOAJInChI 1 3ClH Cr h3 1H q 3 p 3Key QSWDMMVNRMROPK DFZHHIFOAFSMILES Cl Cr Cl ClPropertiesChemical formula CrCl3Molar mass 158 36 g mol anhydrous 266 45 g mol hexahydrate 1 Appearance purple anhydrous dark green hexahydrate Density 2 87 g cm3 anhydrous 1 760 g cm3 hexahydrate Melting point 1 152 C 2 106 F 1 425 K anhydrous 81 C hexahydrate 2 Boiling point 1 300 C 2 370 F 1 570 K decomposesSolubility in water slightly soluble anhydrous 585 g L hexahydrate Solubility insoluble in ethanol insoluble in ether acetoneAcidity pKa 2 4 0 2M solution Magnetic susceptibility x 6890 0 10 6 cm3 molStructureCrystal structure YCl3 structureCoordination geometry OctahedralHazardsGHS labelling PictogramsSignal word DangerHazard statements H302 H314 H411Precautionary statements P260 P264 P270 P273 P280 P301 P312 P301 P330 P331 P303 P361 P353 P304 P340 P305 P351 P338 P310 P321 P330 P363 P391 P405 P501NFPA 704 fire diamond 5 300Flash point Non flammableLethal dose or concentration LD LC LD50 median dose 1870 mg kg oral rat 4 NIOSH US health exposure limits PEL Permissible TWA 1 mg m3 3 REL Recommended TWA 0 5 mg m3 3 IDLH Immediate danger 250 mg m3 3 Safety data sheet SDS ICSC 1316 anhydrous ICSC 1532 hexahydrate Related compoundsOther anions Chromium III fluorideChromium III bromideChromium III iodideOther cations Molybdenum III chlorideTungsten III chlorideRelated compounds Chromium II chlorideChromium IV chlorideExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Contents 1 Structure 1 1 Chromium III chloride hydrates 2 Preparation 3 Reactions 3 1 Complexes with organic ligands 3 2 Precursor to organochromium complexes 3 3 Use in organic synthesis 3 4 Dyestuffs 4 Precautions 5 References 6 Further reading 7 External linksStructure EditAnhydrous chromium III chloride adopts the YCl3 structure with Cr3 occupying one third of the octahedral interstices in alternating layers of a pseudo cubic close packed lattice of Cl ions The absence of cations in alternate layers leads to weak bonding between adjacent layers For this reason crystals of CrCl3 cleave easily along the planes between layers which results in the flaky micaceous appearance of samples of chromium III chloride 6 7 If pressurized to 9 9 GPa it goes under a phase transition 8 Space filling model of cubic close packing of chloride ions in the crystal structure of CrCl3 Ball and stick model of part of a layer Stacking of layers Chromium III chloride hydrates Edit The hydrated chromium III chlorides display the somewhat unusual property of existing in a number of distinct chemical forms isomers which differ in terms of the number of chloride anions that are coordinated to Cr III and the water of crystallization The different forms exist both as solids and in aqueous solutions Several members are known of the series of CrCl3 z H2O n z The common hexahydrate can be more precisely described as CrCl2 H2O 4 Cl 2 H2O It consists of the cation trans CrCl2 H2O 4 and additional molecules of water and a chloride anion in the lattice 9 Two other hydrates are known pale green CrCl H2O 5 Cl2 H2O and violet Cr H2O 6 Cl3 Similar isomerism is seen with other chromium III compounds Preparation EditAnhydrous chromium III chloride may be prepared by chlorination of chromium metal directly or indirectly by carbothermic chlorination of chromium III oxide at 650 800 C 10 11 Cr2O3 3 C 3 Cl2 2 CrCl3 3 COThe hydrated chlorides are prepared by treatment of chromate with hydrochloric acid and aqueous methanol Reactions EditSlow reaction rates are common with chromium III complexes The low reactivity of the d3 Cr3 ion can be explained using crystal field theory One way of opening CrCl3 up to substitution in solution is to reduce even a trace amount to CrCl2 for example using zinc in hydrochloric acid This chromium II compound undergoes substitution easily and it can exchange electrons with CrCl3 via a chloride bridge allowing all of the CrCl3 to react quickly With the presence of some chromium II however solid CrCl3 dissolves rapidly in water Similarly ligand substitution reactions of solutions of CrCl2 H2O 4 are accelerated by chromium II catalysts With molten alkali metal chlorides such as potassium chloride CrCl3 gives salts of the type M3CrCl6 and K3Cr2Cl9 which is also octahedral but where the two chromiums are linked via three chloride bridges The hexahydrate can also be dehydrated with thionyl chloride 12 CrCl3 6 H2O 6 SOCl2 CrCl3 6 SO2 12 HClComplexes with organic ligands Edit CrCl3 is a Lewis acid classified as hard according to the Hard Soft Acid Base theory It forms a variety of adducts of the type CrCl3L3 z where L is a Lewis base For example it reacts with pyridine C5 H5 N to form the pyridine complex CrCl3 3 C5H5N CrCl3 C5H5N 3Treatment with trimethylsilylchloride in THF gives the anhydrous THF complex 13 CrCl3 6 H2O 12 Me3SiCl CrCl3 THF 3 6 Me3Si 2O 12 HClPrecursor to organochromium complexes Edit Chromium III chloride is used as the precursor to many organochromium compounds for example bis benzene chromium an analogue of ferrocene Phosphine complexes derived from CrCl3 catalyse the trimerization of ethylene to 1 hexene 14 15 Use in organic synthesis Edit One niche use of CrCl3 in organic synthesis is for the in situ preparation of chromium II chloride a reagent for the reduction of alkyl halides and for the synthesis of E alkenyl halides The reaction is usually performed using two moles of CrCl3 per mole of lithium aluminium hydride although if aqueous acidic conditions are appropriate zinc and hydrochloric acid may be sufficient Chromium III chloride has also been used as a Lewis acid in organic reactions for example to catalyse the nitroso Diels Alder reaction 16 Dyestuffs Edit A number of chromium containing dyes are used commercially for wool Typical dyes are triarylmethanes consisting of ortho hydroxylbenzoic acid derivatives 17 Precautions EditAlthough trivalent chromium is far less poisonous than hexavalent chromium salts are generally considered toxic References Edit Chromium III chloride sublimation 99 10025 73 7 Chromium III chloride hexahydrate Technipur Sigma Aldrich Retrieved 2022 08 16 a b c NIOSH Pocket Guide to Chemical Hazards 0141 National Institute for Occupational Safety and Health NIOSH Chromium III compounds as Cr III Immediately Dangerous to Life or Health Concentrations IDLH National Institute for Occupational Safety and Health NIOSH Cameo Chemicals MSDS Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann p 1020 ISBN 978 0 08 037941 8 A F Wells Structural Inorganic Chemistry 5th ed Oxford University Press Oxford UK 1984 Meiling Hong 2022 Pressure Induced Structural Phase Transition and Metallization of CrCl3 under Different Hydrostatic Environments up to 50 0 GPa Inorg Chem 61 12 4852 4864 doi 10 1021 acs inorgchem 1c03486 PMID 35289613 S2CID 247452267 Ian G Dance Hans C Freeman The Crystal Structure of Dichlorotetraaquochromium III Chloride Dihydrate Primary and Secondary Metal Ion Hydration Inorganic Chemistry 1965 volume 4 1555 1561 doi 10 1021 ic50033a006 D Nicholls Complexes and First Row Transition Elements Macmillan Press London 1973 Brauer Georg 1965 1962 Handbuch Der Praparativen Anorganischen Chemie Handbook of Preparative Inorganic Chemistry in German Vol 2 Stuttgart New York New York Ferdinand Enke Verlag Academic Press Inc p 1340 ISBN 978 0 32316129 9 Retrieved 2014 01 10 Pray A P 1990 Anhydrous Metal Chlorides Inorganic Syntheses Inorganic Syntheses Vol 28 p 321 2 doi 10 1002 9780470132401 ch36 ISBN 9780470132401 Philip Boudjouk Jeung Ho So 1992 Solvated and Unsolvated Anhydrous Metal Chlorides from Metal Chloride Hydrates Inorganic Syntheses Inorganic Syntheses Vol 29 pp 108 111 doi 10 1002 9780470132609 ch26 ISBN 9780470132609 a href Template Cite book html title Template Cite book cite book a CS1 maint uses authors parameter link John T Dixon Mike J Green Fiona M Hess David H Morgan Advances in selective ethylene trimerisation a critical overview Journal of Organometallic Chemistry 2004 Volume 689 pp 3641 3668 doi 10 1016 j jorganchem 2004 06 008 Feng Zheng Akella Sivaramakrishna John R Moss Thermal studies on metallacycloalkanes Coordination Chemistry Reviews 2007 Volume 251 2056 2071 doi 10 1016 j ccr 2007 04 008 Calvet G Dussaussois M Blanchard N Kouklovsky C 2004 Lewis Acid Promoted Hetero Diels Alder Cycloaddition of a Acetoxynitroso Dienophiles Organic Letters 6 14 2449 2451 doi 10 1021 ol0491336 PMID 15228301 Thomas Gessner and Udo Mayer Triarylmethane and Diarylmethane Dyes in Ullmann s Encyclopedia of Industrial Chemistry 2002 Wiley VCH Weinheim doi 10 1002 14356007 a27 179Further reading EditHandbook of Chemistry and Physics 71st edition CRC Press Ann Arbor Michigan 1990 The Merck Index 7th edition Merck amp Co Rahway New Jersey USA 1960 J March Advanced Organic Chemistry 4th ed p 723 Wiley New York 1992 K Takai in Handbook of Reagents for Organic Synthesis Volume 1 Reagents Auxiliaries and Catalysts for C C Bond Formation R M Coates S E Denmark eds pp 206 211 Wiley New York 1999 External links Edit Wikimedia Commons has media related to Chromium III chloride International Chemical Safety Card 1316 anhydr CrCl3 International Chemical Safety Card 1532 CrCl3 6H2O National Pollutant Inventory Chromium III compounds fact sheet NIOSH Pocket Guide to Chemical Hazards IARC Monograph Chromium and Chromium compounds Retrieved from https en wikipedia org w index php title Chromium III chloride amp oldid 1137331913, wikipedia, wiki, book, books, library,
