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{{chembox
{{chembox
| Verifiedfields = changed
| Verifiedfields = changed
| Watchedfields = changed
| Watchedfields = changed
| verifiedrevid = 444348698
| verifiedrevid = 444348698
| Name = Tin(II) chloride
| Name = Tin(II) chloride
| ImageFile = Tin(II) chloride.jpg
| ImageFile = Tin(II) chloride.jpg
| ImageFileL1 = Tin-dichloride-gas-molecule-3D-balls.png
⚫
| ImageName = Tin(II) chloride
| IUPACName = Tin(II) chloride<br/>Tin dichloride
| ImageFileR1 = Tin(II) chloride space-filling3D.png
⚫
| ImageName = Tin(II) chloride
⚫
| OtherNames = Stannous chloride<br/>Tin salt<br/>Tin protochloride
| ImageCaptionL1 = Ball-and-stick model (gas phase).
| ImageCaptionR1 = Space-filling model (gas phase).
| IUPACName = Tin(II) chloride<br/>Tin dichloride
⚫
| OtherNames = {{Unbulleted list|Stannous chloride|Tin salt|Tin protochloride}}
| data page pagename = none
| SystematicName =
| SystematicName =
| Section1 = {{Chembox Identifiers
| Section1 = {{Chembox Identifiers
| CASNo = 7772-99-8
| CASNo = 7772-99-8
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo_Ref = {{cascite|correct|CAS}}
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| StdInChIKey = AXZWODMDQAVCJE-UHFFFAOYSA-L
| StdInChIKey = AXZWODMDQAVCJE-UHFFFAOYSA-L
}}
}}
| Section2 = {{Chembox Properties
| Section2 = {{Chembox Properties
| Formula = Cl<sub>2</sub>An
| Formula = SnCl<sub>2</sub>
| MolarMass = 189.60 g/mol (anhydrous)<br />225.63 g/mol (dihydrate)
| MolarMass = 189.60 g/mol (anhydrous)<br />225.63 g/mol (dihydrate)
| Appearance = White crystalline solid
| Appearance = White crystalline solid
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| MagSus = &minus;69.0·10<sup>−6</sup> cm<sup>3</sup>/mol
| MagSus = &minus;69.0·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
}}
| Section3 = {{Chembox Structure
| Section3 = {{Chembox Structure
| MolShape = [[Bent molecular geometry|Bent]] (gas phase)
| MolShape = [[Bent molecular geometry|Bent]] (gas phase)
| Coordination = [[Trigonal pyramidal]] (anhydrous)<br/>Dihydrate also three-coordinate
| Coordination = [[Trigonal pyramidal]] (anhydrous)<br/>Dihydrate also three-coordinate
| CrystalStruct = Layer structure<br/>(chains of SnCl<sub>3</sub> groups)
| CrystalStruct = Layer structure<br/>(chains of SnCl<sub>3</sub> groups)
}}
}}
| Section4 = {{Chembox Thermochemistry
| Section4 = {{Chembox Thermochemistry
| DeltaHf = &minus;325 kJ/mol
| DeltaHf = &minus;325 kJ/mol
}}
}}
| Section7 = {{Chembox Hazards
| Section7 = {{Chembox Hazards
| ExternalSDS = [https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0955&p_version=2 ICSC 0955 (anhydrous)]<br/>[https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0738&p_version=2 ICSC 0738 (dihydrate)]
| ExternalSDS = [https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0955&p_version=2 ICSC 0955 (anhydrous)]<br/>[https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0738&p_version=2 ICSC 0738 (dihydrate)]
| MainHazards = Irritant, dangerous for aquatic organisms
| MainHazards = Irritant, dangerous for aquatic organisms
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| LD50 = 700 mg/kg (rat, oral)<br/>10,000 mg/kg (rabbit, oral)<br/>250 mg/kg (mouse, oral)<ref>{{IDLH|7440315|Tin (inorganic compounds, as Sn)}}</ref>
| LD50 = 700 mg/kg (rat, oral)<br/>10,000 mg/kg (rabbit, oral)<br/>250 mg/kg (mouse, oral)<ref>{{IDLH|7440315|Tin (inorganic compounds, as Sn)}}</ref>
}}
}}
| Section8 = {{Chembox Related
| Section8 = {{Chembox Related
| OtherAnions = [[Tin(II) fluoride]]<br/>[[Tin(II) bromide]]<br/>[[Tin(II) iodide]]
| OtherAnions = [[Tin(II) fluoride]]<br/>[[Tin(II) bromide]]<br/>[[Tin(II) iodide]]
| OtherCations = [[Germanium dichloride]]<br/>[[Tin(IV) chloride]]<br/>[[Lead(II) chloride]]
| OtherCations = [[Germanium dichloride]]<br/>[[Tin(IV) chloride]]<br/>[[Lead(II) chloride]]
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==Chemical structure==
==Chemical structure==
SnCl<sub>2</sub> has a [[lone pair]] of [[electron]]s, such that the molecule in the gas phase is bent. In the solid state, crystalline SnCl<sub>2</sub> forms chains linked via [[chloride]] bridges as shown. The dihydrate is also three-coordinate, with one water coordinated on to the tin, and a second water coordinated to the first. The main part of the molecule stacks into double layers in the [[crystal lattice]], with the "second" water sandwiched between the layers.
SnCl<sub>2</sub> has a [[lone pair]] of [[electron]]s, such that the molecule in the gas phase is bent. In the solid state, crystalline SnCl<sub>2</sub> forms chains linked via [[chloride]] bridges as shown. The dihydrate has three coordinates as well, with one water on the tin and another water on the first. The main part of the molecule stacks into double layers in the [[crystal lattice]], with the "second" water sandwiched between the layers.


[[Image:SnCl2 structure.svg|thumb|460px|left|Structures of tin(II) chloride and related compounds]]
[[Image:SnCl2 structure.svg|thumb|460px|left|Structures of tin(II) chloride and related compounds]]
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==Chemical properties==
==Chemical properties==
Tin(II) chloride can dissolve in less than its own mass of water without apparent decomposition, but as the solution is diluted, hydrolysis occurs to form an insoluble basic salt:
Tin(II) chloride can dissolve in less than its own mass of water without apparent decomposition, but as the solution is diluted, hydrolysis occurs to form an insoluble basic salt:

:SnCl<sub>2</sub> (aq) + H<sub>2</sub>O (l) {{eqm}} Sn(OH)Cl (s) + HCl (aq)
:SnCl<sub>2</sub> (aq) + H<sub>2</sub>O (l) {{eqm}} Sn(OH)Cl (s) + HCl (aq)


Therefore, if clear solutions of tin(II) chloride are to be used, it must be dissolved in [[hydrochloric acid]] (typically of the same or greater molarity as the stannous chloride) to maintain the [[chemical equilibrium|equilibrium]] towards the left-hand side (using [[Le Chatelier's principle]]). Solutions of SnCl<sub>2</sub> are also unstable towards [[Redox|oxidation]] by the air:
Therefore, if clear solutions of tin(II) chloride are to be used, it must be dissolved in [[hydrochloric acid]] (typically of the same or greater molarity as the stannous chloride) to maintain the [[chemical equilibrium|equilibrium]] towards the left-hand side (using [[Le Chatelier's principle]]). Solutions of SnCl<sub>2</sub> are also unstable towards [[Redox|oxidation]] by the air:

:6 SnCl<sub>2</sub> (aq) + O<sub>2</sub> (g) + 2 H<sub>2</sub>O (l) → 2 SnCl<sub>4</sub> (aq) + 4 Sn(OH)Cl (s)
:6 SnCl<sub>2</sub> (aq) + O<sub>2</sub> (g) + 2 H<sub>2</sub>O (l) → 2 SnCl<sub>4</sub> (aq) + 4 Sn(OH)Cl (s)


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There are many such cases where tin(II) chloride acts as a reducing agent, reducing [[silver]] and [[gold]] salts to the metal, and iron(III) salts to iron(II), for example:
There are many such cases where tin(II) chloride acts as a reducing agent, reducing [[silver]] and [[gold]] salts to the metal, and iron(III) salts to iron(II), for example:

:SnCl<sub>2</sub> (aq) + 2 FeCl<sub>3</sub> (aq) → SnCl<sub>4</sub> (aq) + 2 FeCl<sub>2</sub> (aq)
:SnCl<sub>2</sub> (aq) + 2 FeCl<sub>3</sub> (aq) → SnCl<sub>4</sub> (aq) + 2 FeCl<sub>2</sub> (aq)


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Solutions of tin(II) chloride can also serve simply as a source of Sn<sup>2+</sup> ions, which can form other tin(II) compounds via [[precipitation (chemistry)|precipitation]] reactions. For example, reaction with [[sodium sulfide]] produces the brown/black [[tin(II) sulfide]]:
Solutions of tin(II) chloride can also serve simply as a source of Sn<sup>2+</sup> ions, which can form other tin(II) compounds via [[precipitation (chemistry)|precipitation]] reactions. For example, reaction with [[sodium sulfide]] produces the brown/black [[tin(II) sulfide]]:

:SnCl<sub>2</sub> (aq) + Na<sub>2</sub>S (aq) → SnS (s) + 2 NaCl (aq)
:SnCl<sub>2</sub> (aq) + Na<sub>2</sub>S (aq) → SnS (s) + 2 NaCl (aq)


If [[alkali]] is added to a solution of SnCl<sub>2</sub>, a white precipitate of hydrated [[tin(II) oxide]] forms initially; this then dissolves in excess base to form a stannite salt such as sodium stannite:
If [[alkali]] is added to a solution of SnCl<sub>2</sub>, a white precipitate of hydrated [[tin(II) oxide]] forms initially; this then dissolves in excess base to form a stannite salt such as sodium stannite:

:SnCl<sub>2</sub>(aq) + 2 NaOH (aq) → SnO·H<sub>2</sub>O (s) + 2 NaCl (aq)
:SnCl<sub>2</sub>(aq) + 2 NaOH (aq) → SnO·H<sub>2</sub>O (s) + 2 NaCl (aq)

:SnO·H<sub>2</sub>O (s) + NaOH (aq) → NaSn(OH)<sub>3</sub> (aq)
:SnO·H<sub>2</sub>O (s) + NaOH (aq) → NaSn(OH)<sub>3</sub> (aq)


Anhydrous SnCl<sub>2</sub> can be used to make a variety of interesting tin(II) compounds in non-aqueous solvents. For example, the [[lithium]] [[salt (chemistry)|salt]] of [[Butylated hydroxytoluene|4-methyl-2,6-di-tert-butylphenol]] reacts with SnCl<sub>2</sub> in [[Tetrahydrofuran|THF]] to give the yellow linear two-coordinate compound Sn(OAr)<sub>2</sub> (Ar = [[aryl]]).<ref>{{cite journal|author = B. Cetinkaya, I. Gumrukcu, M. F. Lappert, J. L. Atwood, R. D. Rogers and M. J. Zaworotko|title = Bivalent germanium, tin, and lead 2,6-di-tert-butylphenoxides and the crystal and molecular structures of M(OC6H2Me-4-But2-2,6)2 (M = Ge or Sn)|year = 1980|journal = [[J. Am. Chem. Soc.]]|volume = 102|issue = 6|pages = 2088–2089|doi = 10.1021/ja00526a054}}</ref>
Anhydrous SnCl<sub>2</sub> can be used to make a variety of interesting tin(II) compounds in non-aqueous solvents. For example, the [[lithium]] [[salt (chemistry)|salt]] of [[Butylated hydroxytoluene|4-methyl-2,6-di-tert-butylphenol]] reacts with SnCl<sub>2</sub> in [[Tetrahydrofuran|THF]] to give the yellow linear two-coordinate compound Sn(OAr)<sub>2</sub> (Ar = [[aryl]]).<ref>{{Cite journal|last1=Cetinkaya|first1=B.|last2=Gumrukcu|first2=I.|last3=Lappert|first3=M. F.|last4=Atwood|first4=J. L.|last5=Rogers|first5=R. D.|last6=Zaworotko|first6=M. J.|display-authors=3|date=1980-03-01|title=Bivalent germanium, tin, and lead 2,6-di-tert-butylphenoxides and the crystal and molecular structures of M(OC6H2Me-4-But2-2,6)2 (M = Ge or Sn)|url=https://doi.org/10.1021/ja00526a054|journal=[[Journal of the American Chemical Society]]|volume=102|issue=6|pages=2088–2089|doi=10.1021/ja00526a054|issn=0002-7863}}</ref>


Tin(II) chloride also behaves as a [[Lewis acid]], forming [[complex (chemistry)|complexes]] with [[ligand]]s such as [[chloride]] ion, for example:
Tin(II) chloride also behaves as a [[Lewis acid]], forming [[complex (chemistry)|complexes]] with [[ligand]]s such as [[chloride]] ion, for example:

:SnCl<sub>2</sub> (aq) + CsCl (aq) → CsSnCl<sub>3</sub> (aq)
:SnCl<sub>2</sub> (aq) + CsCl (aq) → CsSnCl<sub>3</sub> (aq)


Most of these complexes are [[pyramidal]], and since complexes such as SnCl<sub>3</sub> have a full [[Octet rule|octet]], there is little tendency to add more than one ligand. The [[lone pair]] of electrons in such complexes is available for bonding, however, and therefore the complex itself can act as a [[Lewis base]] or ligand. This seen in the [[ferrocene]]-related product of the following reaction :
Most of these complexes are [[pyramidal]], and since complexes such as SnCl{{su|b=3|p=&minus;}} have a full [[Octet rule|octet]], there is little tendency to add more than one ligand. The [[lone pair]] of electrons in such complexes is available for bonding, however, and therefore the complex itself can act as a [[Lewis base]] or ligand. This seen in the [[ferrocene]]-related product of the following reaction:

:SnCl<sub>2</sub> + Fe(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(CO)<sub>2</sub>HgCl → Fe(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(CO)<sub>2</sub>SnCl<sub>3</sub> + Hg
:SnCl<sub>2</sub> + Fe(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(CO)<sub>2</sub>HgCl → Fe(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(CO)<sub>2</sub>SnCl<sub>3</sub> + Hg


SnCl<sub>2</sub> can be used to make a variety of such compounds containing metal-metal bonds. For example, the reaction with [[dicobalt octacarbonyl]]:
SnCl<sub>2</sub> can be used to make a variety of such compounds containing metal-metal bonds. For example, the reaction with [[dicobalt octacarbonyl]]:

:SnCl<sub>2</sub> + Co<sub>2</sub>(CO)<sub>8</sub> → (CO)<sub>4</sub>Co-(SnCl<sub>2</sub>)-Co(CO)<sub>4</sub>
:SnCl<sub>2</sub> + Co<sub>2</sub>(CO)<sub>8</sub> → (CO)<sub>4</sub>Co-(SnCl<sub>2</sub>)-Co(CO)<sub>4</sub>


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:Sn (s) + 2 HCl (aq) → SnCl<sub>2</sub> (aq) + {{chem2|H2}} (g)
:Sn (s) + 2 HCl (aq) → SnCl<sub>2</sub> (aq) + {{chem2|H2}} (g)


The water then carefully evaporated from the acidic solution to produce crystals of SnCl<sub>2</sub>·2H<sub>2</sub>O. This dihydrate can be [[dehydration reaction|dehydrated]] to anhydrous using [[acetic anhydride]].<ref>{{cite book|author1=W. L. F. Armarego |author2=C. L. L. Chai |title = Purification of laboratory chemicals|publisher = Butterworth-Heinemann|edition = 6|location = The United States of America|year = 2009}}</ref>
The water then carefully evaporated from the acidic solution to produce crystals of SnCl<sub>2</sub>·2H<sub>2</sub>O. This dihydrate can be [[dehydration reaction|dehydrated]] to anhydration using [[acetic anhydride]].<ref>{{Cite book |last1=Armarego |first1=W. L. F. |url=https://www.abebooks.com/9781856175678/Purification-Laboratory-Chemicals-Armarego-W.L.F-1856175677/plp |title=Purification of Laboratory Chemicals |last2=Chai |first2=C. L. L. |publisher=[[Elsevier]], Butterwoth-Heinemann |year=2009 |isbn=978-0-08-087824-9 |location=Burlington |language=en |doi=10.1016/B978-1-85617-567-8.50009-3 |access-date=2022-02-03}}</ref>


==Uses==
==Uses==
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Tin(II) chloride is used as a [[mordant]] in textile [[dyeing]] because it gives brighter colours with some dyes e.g. [[cochineal]]. This mordant has also been used alone to increase the weight of silk.
Tin(II) chloride is used as a [[mordant]] in textile [[dyeing]] because it gives brighter colours with some dyes e.g. [[cochineal]]. This mordant has also been used alone to increase the weight of silk.


In recent years, an increasing number of [[tooth paste]] brands has been adding Tin(II) chloride as protection against enamel erosion to their formula, e. g. [[Oral-B]] or [[Elmex]].
In recent years, an increasing number of [[tooth paste]] brands have been adding Tin(II) chloride as protection against enamel erosion to their formula, e. g. [[Oral-B]] or [[Elmex]].


It is used as a catalyst in the production of the plastic [[polylactic acid]] (PLA).
It is used as a catalyst in the production of the plastic [[polylactic acid]] (PLA).
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It also finds a use as a catalyst between acetone and hydrogen peroxide to form the tetrameric form of [[acetone peroxide]].
It also finds a use as a catalyst between acetone and hydrogen peroxide to form the tetrameric form of [[acetone peroxide]].


Tin(II) chloride also finds wide use as a [[Redox|reducing agent]]. This is seen in its use for silvering mirrors, where [[silver]] metal is deposited on the glass:
Tin(II) chloride also finds wide use as a [[reducing agent]]. This is seen in its use for silvering mirrors, where [[silver]] metal is deposited on the glass:


:Sn<sup>2+</sup> (aq) + 2 Ag<sup>+</sup> → Sn<sup>4+</sup> (aq) + 2 Ag (s)
:Sn<sup>2+</sup> (aq) + 2 Ag<sup>+</sup> → Sn<sup>4+</sup> (aq) + 2 Ag (s)


A related reduction was traditionally used as an analytical test for {{chem2|auto=1|Hg(2+) (aq)}}. For example, if SnCl<sub>2</sub> is added [[wikt:dropwise|dropwise]] into a solution of [[mercury(II) chloride]], a white precipitate of [[mercury(I) chloride]] is first formed; as more SnCl<sub>2</sub> is added this turns black as metallic mercury is formed. Stannous chloride can be used to test for the presence of [[gold]] [[chemical compound|compounds]]. SnCl<sub>2</sub> turns bright [[violet (color)|purple]] in the presence of gold (see ''[[Purple of Cassius]]'').
A related reduction was traditionally used as an analytical test for {{chem2|auto=1|Hg(2+) (aq)}}. For example, if SnCl<sub>2</sub> is added [[wikt:dropwise|dropwise]] into a solution of [[mercury(II) chloride]], a white precipitate of [[mercury(I) chloride]] is first formed; as more SnCl<sub>2</sub> is added this turns black as metallic mercury is formed.

Stannous chloride is also used by many precious metals refining hobbyists and professionals to test for the presence of [[gold]] salts.<ref>{{Citation |title=How To Make Stannous Chloride for Testing Gold Solutions | date=27 February 2015 |url=https://www.youtube.com/watch?v=v--lPph0nog |access-date=2023-02-10 |language=en}}</ref> When SnCl<sub>2</sub> comes into contact with gold compounds, particularly [[Chloroauric acid|chloroaurate]] salts, it forms a bright purple colloid known as [[purple of Cassius]].<ref>{{Cite journal |last1=Fink |first1=Colin |last2=Putnam |first2=Garth |date=1942-06-01 |title=Determination of Small Amounts of Gold with Stannous Chloride |url=https://pubs.acs.org/doi/abs/10.1021/i560106a008 |journal=Industrial & Engineering Chemistry Analytical Edition |language=en |volume=14 |issue=6 |pages=468–470 |doi=10.1021/i560106a008 |issn=0096-4484}}</ref> A similar reaction occurs with [[platinum]] and [[palladium]] salts, becoming green and brown respectively.<ref>{{Cite web |last=Sam |date=2020-07-11 |title=Stannous Chloride – Test For Gold, Platinum and Palladium Presence |url=https://www.goldnscrap.com/post/stannous-chloride-test-for-gold-platinum-and-palladium-presence |access-date=2024-05-05 |website=Gold-N-scrap |language=en}}</ref>


When mercury is analyzed using atomic absorption spectroscopy, a cold vapor method must be used, and tin (II) chloride is typically used as the reductant.
When mercury is analyzed using atomic absorption spectroscopy, a cold vapor method must be used, and tin (II) chloride is typically used as the reductant.
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The Stephen reduction is less used today, because it has been mostly superseded by [[diisobutylaluminium hydride]] reduction.
The Stephen reduction is less used today, because it has been mostly superseded by [[diisobutylaluminium hydride]] reduction.


Additionally, SnCl<sub>2</sub> is used to selectively reduce [[aromatic]] [[nitro compound|nitro]] groups to [[aniline]]s.<ref>{{cite journal|author1=F. D. Bellamy |author2=K. Ou |name-list-style=amp |title = Selective reduction of aromatic nitro compounds with stannous chloride in non acidic and non aqueous medium|year = 1984|journal = [[Tetrahedron Letters]]|volume = 25|issue = 8|pages = 839–842|doi = 10.1016/S0040-4039(01)80041-1}}</ref>
Additionally, SnCl<sub>2</sub> is used to selectively reduce [[aromatic]] [[nitro compound|nitro]] groups to [[aniline]]s.<ref>{{cite journal|author1=F. D. Bellamy |author2=K. Ou |name-list-style=amp |title = Selective reduction of aromatic nitro compounds with stannous chloride in non-acidic and non-aqueous medium|year = 1984|journal = [[Tetrahedron Letters]]|volume = 25|issue = 8|pages = 839–842|doi = 10.1016/S0040-4039(01)80041-1}}</ref>


[[Image:SnCl2 Nitro Reduction Scheme.png|center|350px|Aromatic nitro group reduction using SnCl<sub>2</sub>]]
[[Image:SnCl2 Nitro Reduction Scheme.png|center|350px|Aromatic nitro group reduction using SnCl<sub>2</sub>]]
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SnCl<sub>2</sub> is used in [[radionuclide angiography]] to reduce the radioactive agent [[technetium]]-99m-[[pertechnetate]] to assist in binding to blood cells.
SnCl<sub>2</sub> is used in [[radionuclide angiography]] to reduce the radioactive agent [[technetium]]-99m-[[pertechnetate]] to assist in binding to blood cells.


Molten SnCl<sub>2</sub> can be oxidised to form highly crystalline SnO<sub>2</sub> nanostructures.<ref>{{Cite journal|last1=Kamali|first1=Ali|first2=Reza|last2=Divitini|first3=Giorgio|last3=Ducati|first4=Caterina|last4=Fray|first5=Derek|last5=J|date=2014|title=Transformation of molten SnCl2 to SnO2 nano-single crystals|url=https://www.worldcat.org/oclc/5902254906|journal=CERI Ceramics International|language=English|volume=40|issue=6|pages=8533–8538|doi=10.1016/j.ceramint.2014.01.067|issn=0272-8842|oclc=5902254906}}</ref><ref>{{Cite journal|last=Kamali|first=Ali Reza|date=2014|title=Thermokinetic characterisation of tin(II) chloride|url=https://www.worldcat.org/oclc/5690448892|journal=Journal of Thermal Analysis and Calorimetry |language=English|volume=118|issue=1|pages=99–104|doi=10.1007/s10973-014-4004-z|s2cid=98207611|issn=1388-6150|oclc=5690448892}}</ref>
Aqueous stannous chloride is used by many precious metals refining hobbyists and professionals as an indicator of [[gold]] and [[platinum group metals]] in solutions.<ref>[https://www.youtube.com/watch?v=v--lPph0nog How To Make Stannous Chloride for Testing Gold Solutions - YouTube<!-- Bot generated title -->]</ref>


A Stannous reduction is used in [[nuclear medicine]] [[bone scintigraphy|bone scans]] to remove the negative charge from free [[pertechnetate]] when it is bound to MDP for radiopharmaceutical studies. Incomplete reduction due to insufficient tin or accidental insufflation of air leads to the formation of free pertechnetate, a finding which can be seen on bone scans due to its inappropriate uptake in the stomach.<ref>{{cite journal |last1=Cabral |first1=RE |last2=Leitão |first2=AC |last3=Lage |first3=C |last4=Caldeira-de-Araújo |first4=A |last5=Bernardo-Filho |first5=M |last6=Dantas |first6=FJ |last7=Cabral-Neto |first7=JB |title=Mutational potentiality of stannous chloride: an important reducing agent in the Tc-99m-radiopharmaceuticals. |journal=Mutation Research |date=7 August 1998 |volume=408 |issue=2 |pages=129–35 |doi=10.1016/s0921-8777(98)00026-3 |pmid=9739815}}</ref>
Molten SnCl<sub>2</sub> can be oxidised to form highly crystalline SnO<sub>2</sub> nanostructures.<ref>A.R.Kamali, Thermokinetic characterisation of tin(11) chloride, J Therm Anal Calorim 118(2014) 99-104.</ref><ref>A.R.Kamali et al.Transformation of molten SnCl<sub>2</sub> to SnO<sub>2</sub> nano-single crystals, Ceram Intern 40 (2014)8533-8538.</ref>

Stannous Chloride is used for coating SnO<sub>2</sub> Tin Oxide doped conductive [[iridescent]] coatings for low e glass. <ref>Electrically conducting coating on glass and other ceramic bodies https://patents.google.com/patent/US2564987A/en</ref>


==Notes==
==Notes==
⚫
{{reflist}}

⚫
==References==
* N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
* N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
* ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
* ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
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* A. F. Wells, '''Structural Inorganic Chemistry'', 5th ed., Oxford University Press, Oxford, UK, 1984.
* A. F. Wells, '''Structural Inorganic Chemistry'', 5th ed., Oxford University Press, Oxford, UK, 1984.
* J. March, ''Advanced Organic Chemistry'', 4th ed., p.&nbsp;723, Wiley, New York, 1992.
* J. March, ''Advanced Organic Chemistry'', 4th ed., p.&nbsp;723, Wiley, New York, 1992.

⚫
==References==
⚫
{{reflist}}


{{Tin compounds}}
{{Tin compounds}}
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[[Category:Metal halides]]
[[Category:Metal halides]]
[[Category:Chlorides]]
[[Category:Chlorides]]
[[Category:Tin compounds]]
[[Category:Tin(II) compounds]]
[[Category:Coordination complexes]]
[[Category:Coordination complexes]]
[[Category:Deliquescent substances]]
[[Category:Deliquescent materials]]
[[Category:Reducing agents]]
[[Category:Reducing agents]]
[[Category:E-number additives]]
[[Category:E-number additives]]

Latest revision as of 16:40, 29 October 2024

Tin(II) chloride
Tin(II) chloride
Ball-and-stick model (gas phase).
Space-filling model (gas phase).
Names
IUPAC names
Tin(II) chloride
Tin dichloride
Other names
  • Stannous chloride
  • Tin salt
  • Tin protochloride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
DrugBank
ECHA InfoCard 100.028.971 Edit this at Wikidata
EC Number
  • 231-868-0
E number E512 (acidity regulators, ...)
RTECS number
  • XP8700000 (anhydrous)
    XP8850000 (dihydrate)
UNII
UN number 3260
  • InChI=1S/2ClH.Sn/h2*1H;/q;;+2/p-2 ☒N
    Key: AXZWODMDQAVCJE-UHFFFAOYSA-L ☒N
  • InChI=1/2ClH.Sn/h2*1H;/q;;+2/p-2
    Key: AXZWODMDQAVCJE-NUQVWONBAJ
  • Cl[Sn]Cl
Properties
SnCl2
Molar mass 189.60 g/mol (anhydrous)
225.63 g/mol (dihydrate)
Appearance White crystalline solid
Odor odorless
Density 3.95 g/cm3 (anhydrous)
2.71 g/cm3 (dihydrate)
Melting point 247 °C (477 °F; 520 K) (anhydrous)
37.7 °C (dihydrate)
Boiling point 623 °C (1,153 °F; 896 K) (decomposes)
83.9 g/100 ml (0 °C)
Hydrolyses in hot water
Solubility soluble in ethanol, acetone, ether, Tetrahydrofuran
insoluble in xylene
−69.0·10−6 cm3/mol
Structure
Layer structure
(chains of SnCl3 groups)
Trigonal pyramidal (anhydrous)
Dihydrate also three-coordinate
Bent (gas phase)
Thermochemistry
−325 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Irritant, dangerous for aquatic organisms
GHS labelling:[2]
GHS05: Corrosive GHS07: Exclamation mark GHS08: Health hazard
Danger
H290, H302+H332, H314, H317, H335, H373, H412
P260, P273, P280, P303+P361+P353, P304+P340+P312, P305+P351+P338+P310
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
Lethal dose or concentration (LD, LC):
700 mg/kg (rat, oral)
10,000 mg/kg (rabbit, oral)
250 mg/kg (mouse, oral)[1]
Safety data sheet (SDS) ICSC 0955 (anhydrous)
ICSC 0738 (dihydrate)
Related compounds
Other anions
 Tin(II) fluoride
Tin(II) bromide
Tin(II) iodide
Other cations
 Germanium dichloride
Tin(IV) chloride
Lead(II) 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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Tin(II) chloride, also known as stannous chloride, is a white crystalline solid with the formula SnCl2. It forms a stable dihydrate, but aqueous solutions tend to undergo hydrolysis, particularly if hot. SnCl2 is widely used as a reducing agent (in acid solution), and in electrolytic baths for tin-plating. Tin(II) chloride should not be confused with the other chloride of tin; tin(IV) chloride or stannic chloride (SnCl4).

Chemical structure

[edit]

SnCl2 has a lone pair of electrons, such that the molecule in the gas phase is bent. In the solid state, crystalline SnCl2 forms chains linked via chloride bridges as shown. The dihydrate has three coordinates as well, with one water on the tin and another water on the first. The main part of the molecule stacks into double layers in the crystal lattice, with the "second" water sandwiched between the layers.

Structures of tin(II) chloride and related compounds
Ball-and-stick models of the crystal structure of SnCl2[3]

Chemical properties

[edit]

Tin(II) chloride can dissolve in less than its own mass of water without apparent decomposition, but as the solution is diluted, hydrolysis occurs to form an insoluble basic salt:

SnCl2 (aq) + H2O (l) ⇌ Sn(OH)Cl (s) + HCl (aq)

Therefore, if clear solutions of tin(II) chloride are to be used, it must be dissolved in hydrochloric acid (typically of the same or greater molarity as the stannous chloride) to maintain the equilibrium towards the left-hand side (using Le Chatelier's principle). Solutions of SnCl2 are also unstable towards oxidation by the air:

6 SnCl2 (aq) + O2 (g) + 2 H2O (l) → 2 SnCl4 (aq) + 4 Sn(OH)Cl (s)

This can be prevented by storing the solution over lumps of tin metal.[4]

There are many such cases where tin(II) chloride acts as a reducing agent, reducing silver and gold salts to the metal, and iron(III) salts to iron(II), for example:

SnCl2 (aq) + 2 FeCl3 (aq) → SnCl4 (aq) + 2 FeCl2 (aq)

It also reduces copper(II) to copper(I).

Solutions of tin(II) chloride can also serve simply as a source of Sn2+ ions, which can form other tin(II) compounds via precipitation reactions. For example, reaction with sodium sulfide produces the brown/black tin(II) sulfide:

SnCl2 (aq) + Na2S (aq) → SnS (s) + 2 NaCl (aq)

If alkali is added to a solution of SnCl2, a white precipitate of hydrated tin(II) oxide forms initially; this then dissolves in excess base to form a stannite salt such as sodium stannite:

SnCl2(aq) + 2 NaOH (aq) → SnO·H2O (s) + 2 NaCl (aq)
SnO·H2O (s) + NaOH (aq) → NaSn(OH)3 (aq)

Anhydrous SnCl2 can be used to make a variety of interesting tin(II) compounds in non-aqueous solvents. For example, the lithium salt of 4-methyl-2,6-di-tert-butylphenol reacts with SnCl2 in THF to give the yellow linear two-coordinate compound Sn(OAr)2 (Ar = aryl).[5]

Tin(II) chloride also behaves as a Lewis acid, forming complexes with ligands such as chloride ion, for example:

SnCl2 (aq) + CsCl (aq) → CsSnCl3 (aq)

Most of these complexes are pyramidal, and since complexes such as SnCl−
3 have a full octet, there is little tendency to add more than one ligand. The lone pair of electrons in such complexes is available for bonding, however, and therefore the complex itself can act as a Lewis base or ligand. This seen in the ferrocene-related product of the following reaction:

SnCl2 + Fe(η5-C5H5)(CO)2HgCl → Fe(η5-C5H5)(CO)2SnCl3 + Hg

SnCl2 can be used to make a variety of such compounds containing metal-metal bonds. For example, the reaction with dicobalt octacarbonyl:

SnCl2 + Co2(CO)8 → (CO)4Co-(SnCl2)-Co(CO)4

Preparation

[edit]

Anhydrous SnCl2 is prepared by the action of dry hydrogen chloride gas on tin metal. The dihydrate is made by a similar reaction, using hydrochloric acid:

Sn (s) + 2 HCl (aq) → SnCl2 (aq) + H2 (g)

The water then carefully evaporated from the acidic solution to produce crystals of SnCl2·2H2O. This dihydrate can be dehydrated to anhydration using acetic anhydride.[6]

Uses

[edit]

A solution of tin(II) chloride containing a little hydrochloric acid is used for the tin-plating of steel, in order to make tin cans. An electric potential is applied, and tin metal is formed at the cathode via electrolysis.

Tin(II) chloride is used as a mordant in textile dyeing because it gives brighter colours with some dyes e.g. cochineal. This mordant has also been used alone to increase the weight of silk.

In recent years, an increasing number of tooth paste brands have been adding Tin(II) chloride as protection against enamel erosion to their formula, e. g. Oral-B or Elmex.

It is used as a catalyst in the production of the plastic polylactic acid (PLA).

It also finds a use as a catalyst between acetone and hydrogen peroxide to form the tetrameric form of acetone peroxide.

Tin(II) chloride also finds wide use as a reducing agent. This is seen in its use for silvering mirrors, where silver metal is deposited on the glass:

Sn2+ (aq) + 2 Ag+ → Sn4+ (aq) + 2 Ag (s)

A related reduction was traditionally used as an analytical test for Hg2+ (aq). For example, if SnCl2 is added dropwise into a solution of mercury(II) chloride, a white precipitate of mercury(I) chloride is first formed; as more SnCl2 is added this turns black as metallic mercury is formed.

Stannous chloride is also used by many precious metals refining hobbyists and professionals to test for the presence of gold salts.[7] When SnCl2 comes into contact with gold compounds, particularly chloroaurate salts, it forms a bright purple colloid known as purple of Cassius.[8] A similar reaction occurs with platinum and palladium salts, becoming green and brown respectively.[9]

When mercury is analyzed using atomic absorption spectroscopy, a cold vapor method must be used, and tin (II) chloride is typically used as the reductant.

In organic chemistry, SnCl2 is mainly used in the Stephen reduction, whereby a nitrile is reduced (via an imidoyl chloride salt) to an imine which is easily hydrolysed to an aldehyde.[10]

The reaction usually works best with aromatic nitriles Aryl-CN. A related reaction (called the Sonn-Müller method) starts with an amide, which is treated with PCl5 to form the imidoyl chloride salt.

The Stephen reduction
The Stephen reduction

The Stephen reduction is less used today, because it has been mostly superseded by diisobutylaluminium hydride reduction.

Additionally, SnCl2 is used to selectively reduce aromatic nitro groups to anilines.[11]

Aromatic nitro group reduction using SnCl2
Aromatic nitro group reduction using SnCl2

SnCl2 also reduces quinones to hydroquinones.

Stannous chloride is also added as a food additive with E number E512 to some canned and bottled foods, where it serves as a color-retention agent and antioxidant.

SnCl2 is used in radionuclide angiography to reduce the radioactive agent technetium-99m-pertechnetate to assist in binding to blood cells.

Molten SnCl2 can be oxidised to form highly crystalline SnO2 nanostructures.[12][13]

A Stannous reduction is used in nuclear medicine bone scans to remove the negative charge from free pertechnetate when it is bound to MDP for radiopharmaceutical studies. Incomplete reduction due to insufficient tin or accidental insufflation of air leads to the formation of free pertechnetate, a finding which can be seen on bone scans due to its inappropriate uptake in the stomach.[14]

Stannous Chloride is used for coating SnO2 Tin Oxide doped conductive iridescent coatings for low e glass. [15]

Notes

[edit]
  • N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
  • 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.
  • A. F. Wells, 'Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
  • J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.

References

[edit]
  1. ^ "Tin (inorganic compounds, as Sn)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  2. ^ Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  3. ^ J. M. Leger; J. Haines; A. Atouf (1996). "The high pressure behaviour of the cotunnite and post-cotunnite phases of PbCl2 and SnCl2". J. Phys. Chem. Solids. 57 (1): 7–16. Bibcode:1996JPCS...57....7L. doi:10.1016/0022-3697(95)00060-7.
  4. ^ H. Nechamkin (1968). The Chemistry of the Elements. New York: McGraw-Hill.
  5. ^ Cetinkaya, B.; Gumrukcu, I.; Lappert, M. F.; et al. (1980-03-01). "Bivalent germanium, tin, and lead 2,6-di-tert-butylphenoxides and the crystal and molecular structures of M(OC6H2Me-4-But2-2,6)2 (M = Ge or Sn)". Journal of the American Chemical Society. 102 (6): 2088–2089. doi:10.1021/ja00526a054. ISSN 0002-7863.
  6. ^ Armarego, W. L. F.; Chai, C. L. L. (2009). Purification of Laboratory Chemicals. Burlington: Elsevier, Butterwoth-Heinemann. doi:10.1016/B978-1-85617-567-8.50009-3. ISBN 978-0-08-087824-9. Retrieved 2022-02-03.
  7. ^ How To Make Stannous Chloride for Testing Gold Solutions, 27 February 2015, retrieved 2023-02-10
  8. ^ Fink, Colin; Putnam, Garth (1942-06-01). "Determination of Small Amounts of Gold with Stannous Chloride". Industrial & Engineering Chemistry Analytical Edition. 14 (6): 468–470. doi:10.1021/i560106a008. ISSN 0096-4484.
  9. ^ Sam (2020-07-11). "Stannous Chloride – Test For Gold, Platinum and Palladium Presence". Gold-N-scrap. Retrieved 2024-05-05.
  10. ^ Williams, J. W. (1955). "β-Naphthaldehyde". Organic Syntheses; Collected Volumes, vol. 3, p. 626.
  11. ^ F. D. Bellamy & K. Ou (1984). "Selective reduction of aromatic nitro compounds with stannous chloride in non-acidic and non-aqueous medium". Tetrahedron Letters. 25 (8): 839–842. doi:10.1016/S0040-4039(01)80041-1.
  12. ^ Kamali, Ali; Divitini, Reza; Ducati, Giorgio; Fray, Caterina; J, Derek (2014). "Transformation of molten SnCl2 to SnO2 nano-single crystals". CERI Ceramics International. 40 (6): 8533–8538. doi:10.1016/j.ceramint.2014.01.067. ISSN 0272-8842. OCLC 5902254906.
  13. ^ Kamali, Ali Reza (2014). "Thermokinetic characterisation of tin(II) chloride". Journal of Thermal Analysis and Calorimetry. 118 (1): 99–104. doi:10.1007/s10973-014-4004-z. ISSN 1388-6150. OCLC 5690448892. S2CID 98207611.
  14. ^ Cabral, RE; Leitão, AC; Lage, C; Caldeira-de-Araújo, A; Bernardo-Filho, M; Dantas, FJ; Cabral-Neto, JB (7 August 1998). "Mutational potentiality of stannous chloride: an important reducing agent in the Tc-99m-radiopharmaceuticals". Mutation Research. 408 (2): 129–35. doi:10.1016/s0921-8777(98)00026-3. PMID 9739815.
  15. ^ Electrically conducting coating on glass and other ceramic bodies https://patents.google.com/patent/US2564987A/en
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