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Nickel(II) chloride#Coordination chemistry

{{chembox

|Verifiedfields = changed

|Watchedfields = changed

|verifiedrevid = 445919159

|Name = Nickel chloride

|ImageFile1 = Nickel(II)-chloride-hexahydrate-sample.jpg

|ImageName1 = Nickel(II) chloride hexahydrate

|ImageCaption1 = Hexahydrate

|ImageFile2 = Anhydrous Nickel(II)-chloride.jpg

|ImageCaption2 = Anhydrous

|IUPACName = Nickel(II) chloride

|OtherNames = Nickelous chloride, nickel(II) salt of hydrochloric acid

|Section1 = {{Chembox Identifiers

|CASNo = 7718-54-9

|CASNo_Ref = {{cascite|correct|CAS}}

|CASNo2_Ref = {{cascite|correct|CAS}}

|CASNo2 = 7791-20-0

|CASNo2_Comment = (hexahydrate)

|ChEBI_Ref = {{ebicite|correct|EBI}}

|ChEBI = 34887

|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

|ChemSpiderID = 22796

|EINECS = 231-743-0

|KEGG_Ref = {{keggcite|correct|kegg}}

|KEGG = C14711

|PubChem = 24385

|RTECS = QR6480000

|UNNumber = 3288 3077

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = 696BNE976J

|UNII2_Ref = {{fdacite|correct|FDA}}

|UNII2 = T8365BUD85

|UNII2_Comment = (hexahydrate)

|SMILES = [Ni+2].[Cl-].[Cl-]

|SMILES_Comment = anhydrous

|SMILES1 = Cl[Ni-4](Cl)([OH2+])([OH2+])([OH2+])[OH2+].O.O

|SMILES1_Comment = hexahydrate

|InChI = 1/2ClH.Ni/h2*1H;/q;;+2/p-2

|InChIKey = QMMRZOWCJAIUJA-NUQVWONBAR

|StdInChI_Ref = {{stdinchicite|correct|chemspider}}

|StdInChI = 1S/2ClH.Ni/h2*1H;/q;;+2/p-2

|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

|StdInChIKey = QMMRZOWCJAIUJA-UHFFFAOYSA-L

}}

|Section2 = {{Chembox Properties

|Formula = NiCl2

|Appearance = yellow-brown crystals
deliquescent (anhydrous)
green crystals (hexahydrate)

|Odor = odorless

|Density = 3.55 g/cm3 (anhydrous)
1.92 g/cm3 (hexahydrate)

|MolarMass = 129.5994 g/mol (anhydrous)
237.69 g/mol (hexahydrate)

|Solubility = anhydrous
67.5 g/100 mL (25 °C) {{cite book| author = Lide, David S.|title =CRC Handbook of Chemistry and Physics, 84th Edition| publisher = CRC Press| year = 2003| isbn = 9780849304842|pages=4–71}}
87.6 g/100 mL (100 °C)

hexahydrate
282.5 g/100 mL (25 °C)
578.5 g/100 mL (100 °C)

|SolubleOther = 0.8 g/100 mL (hydrazine)
soluble in ethylene glycol, ethanol, ammonium hydroxide
insoluble in ammonia, nitric acid

|MeltingPtC = 1001

|MeltingPt_notes = (anhydrous)
140 °C (hexahydrate)

|pKa = 4 (hexahydrate)

|MagSus = +6145.0·10−6 cm3/mol

}}

|Section3 = {{Chembox Structure

|Coordination = octahedral at Ni

|CrystalStruct = Monoclinic

}}

|Section4 = {{Chembox Thermochemistry

|DeltaHf = −316 kJ·mol−1{{cite book| author = Zumdahl, Steven S.|title =Chemical Principles 6th Ed.| publisher = Houghton Mifflin Company| year = 2009| isbn = 978-0-618-94690-7|page=A22}}

|Entropy = 107 J·mol−1·K−1

}}

|Section5 = {{Chembox Hazards

|MainHazards = Very toxic (T+)
Irritant (Xi)
Dangerous for the environment (N)
Carcinogen

|ExternalSDS = [https://fscimage.fishersci.com/msds/16310.htm Fischer Scientific]

|NFPA-H = 3

|NFPA-F = 0

|NFPA-R = 0

|GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}}

|GHSSignalWord = Danger

|HPhrases = {{H-phrases|301|315|317|331|334|341|350i|360D|372|410}}

|PPhrases = {{P-phrases|201|202|260|261|264|270|271|272|273|280|281|285|301+310|302+352|304+340|304+341|308+313|311|314|321|330|332+313|333+313|342+311|362|363|391|403+233|405|501}}

|FlashPt = Non-flammable

|LD50 = 105 mg/kg (rat, oral){{IDLH|7440020|Nickel metal and other compounds (as Ni)}}

}}

|Section6 = {{Chembox Related

|OtherAnions = Nickel(II) fluoride
Nickel(II) bromide
Nickel(II) iodide

|OtherCations = Palladium(II) chloride
Platinum(II) chloride
Platinum(II,IV) chloride
Platinum(IV) chloride

|OtherCompounds = Cobalt(II) chloride
Copper(II) chloride}}

}}

Nickel(II) chloride (or just nickel chloride) is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. Nickel(II) chloride, in various forms, is the most important source of nickel for chemical synthesis. The nickel chlorides are deliquescent, absorbing moisture from the air to form a solution. Nickel salts have been shown to be carcinogenic to the lungs and nasal passages in cases of long-term inhalation exposure.{{cite journal|last1=Grimsrud|first1=Tom K|last2=Andersen|first2=Aage|title=Evidence of carcinogenicity in humans of water-soluble nickel salts|journal=Journal of Occupational Medicine and Toxicology|date=2010|volume=5|issue=1|pages=7|doi=10.1186/1745-6673-5-7|pmid=20377901|pmc=2868037 |doi-access=free }}

Production and syntheses

Large scale production and uses of nickel chloride are associated with the purification of nickel from its ores. It is generated upon extraction nickel matte and residues obtained from roasting refining nickel-containing ores using hydrochloric acid. Electrolysis of nickel chloride solutions are used in the production of nickel metal. Other significant routes to nickel chloride arise from processing of ore concentrates such as various reactions involving copper chlorides:{{cite book |doi=10.1002/14356007.a17_157 |chapter=Nickel |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Kerfoot |first1=Derek G. E. |isbn=978-3-527-30385-4 }}

:{{chem2|NiS + 2 CuCl2 -> NiCl2 + 2 CuCl + S}}

:{{chem2|NiO + 2 HCl -> NiCl2 + H2O}}

=Laboratory routes=

Nickel chloride is not usually prepared in the laboratory because it is inexpensive and has a long shelf-life. The yellowish dihydrate, NiCl2·2H2O, is produced by heating the hexahydrate between 66 and 133 °C.{{cite book|doi=10.1002/9780470132449.ch30|chapter=Anhydrous Nickel(II) Halides and their Tetrakis(ethanol) and 1,2-Dimethoxyethane Complexes|year=1972|last1=Ward|first1=Laird G. L.|title=Inorganic Syntheses|volume=13|pages=154–164|isbn=9780470132449}} The hydrates convert to the anhydrous form upon heating in thionyl chloride or by heating under a stream of HCl gas. Simply heating the hydrates does not afford the anhydrous dichloride.

:{{chem2|NiCl2*6H2O + 6 SOCl2 -> NiCl2 + 6SO2 + 12HCl}}

The dehydration is accompanied by a color change from green to yellow.{{cite book | author = Pray, A. P. | title = Inorganic Syntheses | chapter = Anhydrous Metal Chlorides | series = Inorganic Syntheses | volume = 28 | pages = 321–2 | year = 1990 | doi = 10.1002/9780470132593.ch80| isbn = 9780470132593 }}

In case one needs a pure compound without presence of cobalt, nickel chloride can be obtained by cautiously heating hexaamminenickel chloride:{{cite book|language = Russian | author = Karyakin, Yu.V. |title = Pure chemicals. Manual for laboratory preparation of inorganic substances |edition = Moscow, Leningrad "State Scientific Technical Publishing of Chemical Literature" |year = 1947 |pages=416}}

:\overset{hexammine\atop nickel~chloride}{[Ni(NH3)6]Cl2} ->[175-200^\circ\ce{C}] NiCl2{} + 6NH3

Structure of NiCl<sub>2</sub> and its hydrates

Structure of hydrated nickel chloride based on [[X-ray crystallography. Color code: red = O, green = Cl|thumb|left]]

NiCl2 adopts the CdCl2 structure.Wells, A. F. Structural Inorganic Chemistry, Oxford Press, Oxford, United Kingdom, 1984. In this motif, each Ni2+ center is coordinated to six Cl− centers, and each chloride is bonded to three Ni(II) centers. In NiCl2 the Ni-Cl bonds have "ionic character". Yellow NiBr2 and black NiI2 adopt similar structures, but with a different packing of the halides, adopting the CdI2 motif.

In contrast, NiCl2·6H2O consists of separated trans-[NiCl2(H2O)4] molecules linked more weakly to adjacent water molecules. Only four of the six water molecules in the formula is bound to the nickel, and the remaining two are water of crystallization, so the formula of nickel(II) chloride hexahydrate is [NiCl2(H2O)4]·2H2O. Cobalt(II) chloride hexahydrate has a similar structure. The hexahydrate occurs in nature as the very rare mineral nickelbischofite.

The dihydrate NiCl2·2H2O adopts a structure intermediate between the hexahydrate and the anhydrous forms. It consists of infinite chains of NiCl2, wherein both chloride centers are bridging ligands. The trans sites on the octahedral centers occupied by aquo ligands.B. Morosin "An X-ray diffraction study on nickel(II) chloride dihydrate" Acta Crystallogr. 1967. volume 23, pp. 630-634. {{doi|10.1107/S0365110X67003305}} A tetrahydrate NiCl2·4H2O is also known.

Reactions

Nickel(II) chloride solutions are acidic, with a pH of around 4 due to the hydrolysis of the Ni2+ ion.

=Coordination complexes=

File:Color of various Ni(II) complexes in aqueous solution.jpg)3](2+)}}, {{chem2|[Ni(H2O)5Cl]+}}, {{chem2|[Ni(H2O)6](2+)}}]]

Most of the reactions ascribed to "nickel chloride" involve the hexahydrate, although specialized reactions require the anhydrous form.

Reactions starting from NiCl2·6H2O can be used to form a variety of nickel coordination complexes because the H2O ligands are rapidly displaced by ammonia, amines, thioethers, thiolates, and organophosphines. In some derivatives, the chloride remains within the coordination sphere, whereas chloride is displaced with highly basic ligands. Illustrative complexes include:

class="wikitable"
Complex

! Color

! Magnetism

! Geometry

{{chem2|[Ni(NH3)6]Cl2|link=Hexaamminenickel chloride}}

| blue/violet

| paramagnetic

| octahedral

{{chem2|[Ni(en)3](2+)}}

| violet

| paramagnetic

| octahedral

{{chem2|NiCl2(dppe)|link=Dichloro(1,2-bis(diphenylphosphino)ethane)nickel}}

| orange

| diamagnetic

| square planar

{{chem2|[Ni(CN)4](2−)}}

| colorless

| diamagnetic

| square planar

{{chem2|[NiCl4](2−)|link=Tetrachloronickelate}}

| blue{{cite book |author1=Gill, N. S. |author2=Taylor, F. B. |name-list-style=amp | title = Tetrahalo Complexes of Dipositive Metals in the First Transition Series | series = Inorganic Syntheses | year = 1967 | volume = 9 | pages = 136–142 | doi = 10.1002/9780470132401.ch37 |isbn=9780470132401 }}

| paramagnetic{{cite journal |last1=Gerloch |first1=M. |last2=Slade |first2=R. C. |title=Paramagnetic susceptibilities and anisotropies of nickel(II) ions in ‘tetrahedral’ environments. Part II. Covalency and distortion in tetraethylammonium tetrachloronickelate(II), and bis-(N-isopropyl-salicylaldiminato)nickel(II) |journal=J. Chem. Soc. A |date=1969 |volume=0 |issue=0 |pages=1022–1028 |doi=10.1039/J19690001022}}

| tetrahedral{{cite journal |author1=G. D. Stucky |author2=J. B. Folkers |author3=T. J. Kistenmacher | title = The Crystal and Molecular Structure of Tetraethylammonium Tetrachloronickelate(II) | journal = Acta Crystallographica | year = 1967 | volume = 23 | issue = 6 | pages = 1064–1070 | doi =10.1107/S0365110X67004268}}

NiCl2 is the precursor to acetylacetonate complexes Ni(acac)2(H2O)2 and the benzene-soluble (Ni(acac)2)3, which is a precursor to Ni(1,5-cyclooctadiene)2, an important reagent in organonickel chemistry.

In the presence of water scavengers, hydrated nickel(II) chloride reacts with dimethoxyethane (dme) to form the molecular complex NiCl2(dme)2. The dme ligands in this complex are labile.

=Applications in organic synthesis=

NiCl2 and its hydrate are occasionally useful in organic synthesis.Tien-Yau Luh, Yu-Tsai Hsieh Nickel(II) Chloride" in Encyclopedia of Reagents for Organic Synthesis (L. A. Paquette, Ed.) 2001 J. Wiley & Sons, New York. {{doi|10.1002/047084289X.rn012}}. Article Online Posting Date: April 15, 2001.

  • As a mild Lewis acid, e.g. for the regioselective isomerization of dienols:

::File:Dienol-isomerisation-2D-skeletal.png

  • In combination with CrCl2 for the coupling of an aldehyde and a vinylic iodide to give allylic alcohols.
  • For selective reductions in the presence of LiAlH4, e.g. for the conversion of alkenes to alkanes.
  • As a precursor to Brown's P-1 and P-2 nickel boride catalyst through reaction with NaBH4.
  • As a precursor to finely divided Ni by reduction with Zn, for the reduction of aldehydes, alkenes, and nitro aromatic compounds. This reagent also promotes homo-coupling reactions, that is 2RX → R-R where R = aryl, vinyl.
  • As a catalyst for making dialkyl arylphosphonates from phosphites and aryl iodide, ArI:

::ArI + P(OEt)3 → ArP(O)(OEt)2 + EtI

NiCl2-dme (or NiCl2-glyme) is used due to its increased solubility in comparison to the hexahydrate.{{Cite journal |last1=Cornella |first1=Josep |last2=Edwards |first2=Jacob T. |last3=Qin |first3=Tian |last4=Kawamura |first4=Shuhei |last5=Wang |first5=Jie |last6=Pan |first6=Chung-Mao |last7=Gianatassio |first7=Ryan |last8=Schmidt |first8=Michael |last9=Eastgate |first9=Martin D. |date=2016-02-24 |title=Practical Ni-Catalyzed Aryl–Alkyl Cross-Coupling of Secondary Redox-Active Esters |journal=Journal of the American Chemical Society |volume=138 |issue=7 |pages=2174–2177 |doi=10.1021/jacs.6b00250 |doi-access=free |pmc=4768290 |pmid=26835704}}

File:NiCl2 schemes.tif

Safety

Nickel(II) chloride is irritating upon ingestion, inhalation, skin contact, and eye contact. Prolonged inhalation exposure to nickel and its compounds has been linked to increased cancer risk to the lungs and nasal passages.

References

External links

{{Commons category|Nickel(II) chloride}}

  • [https://www.cdc.gov/niosh/npg/npgd0445.html NIOSH Pocket Guide to Chemical Hazards]
  • {{nist}}

{{Nickel compounds}}

{{Chlorides}}

Category:Nickel compounds

Category:Chlorides

Category:Metal halides

Category:IARC Group 1 carcinogens

Category:Coordination complexes