Tin(II) chloride

Chemical structure

SnCl₂ has a crystal lattice, with the "second" water sandwiched between the layers.

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:

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

Therefore if clear solutions of tin(II) chloride are to be used, oxidation by the air:

6 SnCl₂(aq) + s)

This can be prevented by storing the solution over lumps of tin metal.^[1]

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

SnCl₂(aq) + 2 FeCl₂(aq)

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 brown (or 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 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 THF to give the yellow linear two-coordinate compound Sn(OAr)₂ (Ar = aryl).^[2]

Tin(II) chloride also behaves as a chloride ion, for example:

SnCl₂(aq) + CsCl(aq) → CsSnCl₃(aq)

Most of these complexes are pyramidal, and since complexes such as SnCl₃ have a full 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:

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

Preparation

Anhydrous SnCl₂ is prepared by the action of dry hydrochloric acid:

g)

The water is then carefully evaporated from the acidic solution to produce crystals of SnCl₂·2H₂O. This dihydrate can be acetic anhydride.

Uses

A solution of tin(II) chloride containing a little electrolysis.

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

Tin(II) chloride also finds wide use as a 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 purple in the presence of gold.

This very reaction between stannous chloride and gold was used in episode #215:Clueless of House to affirm gold poisoning.^{[citation needed]}

In aldehyde.^[3]

The reaction usually works best with PCl₅ to form the imidoyl chloride salt.

The Stephen reduction is less used today, because it has been mostly superseded by diisobutylaluminium hydride reduction.

Additionally, SnCl₂ is used to selectively reduce anilines.^[4]

SnCl₂ also reduces hydroquinones.

Stannous chloride is also added as a food additive with antioxidant.

In Popular Culture

This compound was featured in the House, M.D. episode “Clueless,” wherein it was used to detect the presence of gold sodium thiomalate used by the patient’s wife to poison him.^{[citation needed]}

References

• 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.

1. ^ H. Nechamkin (1968). The Chemistry of the Elements. New York: McGraw-Hill. 
2. ^ B. Cetinkaya, I. Gumrukcu, M. F. Lappert, J. L. Atwood, R. D. Rogers and M. J. Zaworotko (1980). "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)". J. Am. Chem. Soc. 102 (6): 2088-2089. doi:10.1021/ja00526a054.
3. ^ Williams, J. W. (1955). "β-Naphthaldehyde". Org. Synth.; Coll. Vol. 3: 626. 
4. ^ F. D. Bellamy and 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.