Lead(II) chloride

Summary

Lead(II) chloride (PbCl2) is an inorganic compound which is a white solid under ambient conditions. It is poorly soluble in water. Lead(II) chloride is one of the most important lead-based reagents. It also occurs naturally in the form of the mineral cotunnite.

Lead(II) chloride
Lead(II) chloride precipitation
Cotunnite structure.png
Names
IUPAC names
Lead(II) chloride
Lead dichloride
Other names
Plumbous chloride
Cotunnite
Identifiers
  • 7758-95-4 checkY
3D model (JSmol)
  • Interactive image
ChEBI
  • CHEBI:88212 ☒N
ChemSpider
  • 22867 checkY
ECHA InfoCard 100.028.950 Edit this at Wikidata
EC Number
  • 231-845-5
  • 166945
UNII
  • 4IL61GN3YI ☒N
  • DTXSID1041059 Edit this at Wikidata
  • InChI=1S/2ClH.Pb/h2*1H;/q;;+2/p-2 checkY
    Key: HWSZZLVAJGOAAY-UHFFFAOYSA-L checkY
  • Cl[Pb]Cl
Properties
PbCl2
Molar mass 278.10 g/mol
Appearance white odorless solid
Density 5.85 g/cm3
Melting point 501 °C (934 °F; 774 K)
Boiling point 950 °C (1,740 °F; 1,220 K)
0.99 g/100 mL (20 °C)[1]
1.7×10−5 (20 °C)
Solubility slightly soluble in dilute HCl, ammonia;
insoluble in alcohol

Soluble in hot water as well as in presence of alkali hydroxide

Soluble in concerntrated HCl (>6M)

−73.8·10−6 cm3/mol
2.199[2]
Structure
Orthorhombic, oP12
Pnma, No. 62
Thermochemistry
135.98 JK−1mol−1
-359.41 kJ/mol
Hazards[4]
GHS labelling:
GHS07: Exclamation markGHS08: Health hazardGHS09: Environmental hazard
Danger
H302, H332, H351, H360, H372, H410
P201, P261, P273, P304+P340, P308+P313, P312, P391
NFPA 704 (fire diamond)
3
0
0
Lethal dose or concentration (LD, LC):
140 mg/kg (guinea pig, oral)[3]
Related compounds
Other anions
Lead(II) fluoride
Lead(II) bromide
Lead(II) iodide
Other cations
Lead(IV) chloride
Tin(II) chloride
Germanium(II) chloride
Related compounds
Thallium(I) chloride
Bismuth chloride
Supplementary data page
Lead(II) chloride (data page)
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

Structure and propertiesEdit

In solid PbCl2, each lead ion is coordinated by nine chloride ions in a tricapped triangular prism formation — six lie at the vertices of a triangular prism and three lie beyond the centers of each rectangular prism face. The 9 chloride ions are not equidistant from the central lead atom, 7 lie at 280–309 pm and 2 at 370 pm.[5] PbCl2 forms white orthorhombic needles.

In the gas phase, PbCl2 molecules have a bent structure with the Cl–Pb–Cl angle being 98° and each Pb–-Cl bond distance being 2.44 Å.[6] Such PbCl2 is emitted from internal combustion engines that use ethylene chloride-tetraethyllead additives for antiknock purposes.

PbCl2 is sparingly soluble in water, solubility product Ksp = 1.7×10−5 at 20 °C. It is one of only 5 commonly water-insoluble chlorides, the other 4 being thallium(I) chloride, silver chloride (AgCl) with Ksp = 1.8×10−10, copper(I) chloride (CuCl) with Ksp = 1.72×10−7 and mercury(I) chloride (Hg2Cl2) with Ksp = 1.3×10−18.[7][8]

OccurrenceEdit

PbCl2 occurs naturally in the form of the mineral cotunnite. It is colorless, white, yellow, or green with a density of 5.3–5.8 g/cm3. The hardness on the Mohs scale is 1.5–2. The crystal structure is orthorhombic dipyramidal and the point group is 2/m 2/m 2/m. Each Pb has a coordination number of 9. Cotunnite occurs near volcanoes: Vesuvius, Italy; Tarapacá, Chile; and Tolbachik, Russia.[9]

SynthesisEdit

Double displacement/MetathesisEdit

Lead(II) chloride precipitates upon addition of aqueous chloride sources (HCl, NaCl, KCl) to lead(II) compounds

Direct ReductionEdit

PbCl2 can be formed by the reduction of copper(II) chloride by lead metal:

  • Pb + CuCl2 → PbCl2 + Cu

Direct chlorinationEdit

PbCl2 also forms by the action of chlorine gas on lead metal:

Pb + Cl2 → PbCl2

ReactionsEdit

Addition of chloride ions to a suspension of PbCl2 gives rise to soluble complex ions. In these reactions the additional chloride (or other ligands) break up the chloride bridges that comprise the polymeric framework of solid PbCl2(s).

PbCl2(s) + Cl → [PbCl3](aq)
PbCl2(s) + 2 Cl → [PbCl4]2−(aq)

PbCl2 reacts with molten NaNO2 to give PbO:

PbCl2(l) + 3 NaNO2 → PbO + NaNO3 + 2 NO + 2 NaCl

PbCl2 is used in synthesis of lead(IV) chloride (PbCl4): Cl2 is bubbled through a saturated solution of PbCl2 in aqueous NH4Cl forming [NH4]2[PbCl6]. The latter is reacted with cold concentrated sulfuric acid (H2SO4) forming PbCl4 as an oil.[11]

Lead(II) chloride is the main precursor for organometallic derivatives of lead, such as plumbocenes.[12] The usual alkylating agents are employed, including Grignard reagents and organolithium compounds:

2 PbCl2 + 4 RLi → R4Pb + 4 LiCl + Pb
2 PbCl2 + 4 RMgBr → R4Pb + Pb + 4 MgBrCl
3 PbCl2 + 6 RMgBr → R3Pb-PbR3 + Pb + 6 MgBrCl[13]

These reactions produce derivatives that are more similar to organosilicon compounds, i.e. that Pb(II) tends to disproportionate upon alkylation.

PbCl2 can be used to produce PbO2 by treating it with sodium hypochlorite (NaClO), forming a reddish-brown precipitate of PbO2.

UsesEdit

  • Molten PbCl2 is used in the synthesis of lead titanate and barium lead titanate ceramics by cation replacement reactions:[14]
    x PbCl2(l) + BaTiO3(s) → Ba1−xPbxTiO3 + x BaCl2
  • PbCl2 is used in production of infrared transmitting glass,[10] and ornamental glass called aurene glass. Aurene glass has an iridescent surface formed by spraying with PbCl2 and reheating under controlled conditions. Stannous chloride (SnCl2) is used for the same purpose.[15]
  • Pb is used in HCl service even though the PbCl2 formed is slightly soluble in HCl. Addition of 6–25% of antimony (Sb) increases corrosion resistance.[16]
  • A basic chloride of lead, PbCl2·Pb(OH)2, is known as Pattinson's white lead and is used as pigment in white paint.[17] Lead paint is now banned as a health hazard in many countries by the White Lead (Painting) Convention, 1921.
  • PbCl2 is an intermediate in refining bismuth (Bi) ore. The ore containing Bi, Pb, and Zn is first treated with molten caustic soda to remove traces of arsenic and tellurium. This is followed by the Parkes process to remove any silver and gold present. The ore now contains Bi, Pb, and Zn. It is treated with Cl2 gas at 500 °C. ZnCl2 forms first and is removed. Then PbCl2 forms and is removed leaving pure Bi. BiCl3 would form last.[18]

ToxicityEdit

Like other soluble lead compounds, exposure to PbCl2 may cause lead poisoning.

ReferencesEdit

  1. ^ NIST-data review 1980 Archived 2014-02-11 at the Wayback Machine
  2. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  3. ^ "Lead compounds (as Pb)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ^ "Classifications - CL Inventory". echa.europa.eu.
  5. ^ Wells A. F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  6. ^ Hargittai, I; Tremmel, J; Vajda, E; Ishchenko, A; Ivanov, A; Ivashkevich, L; Spiridonov, V (1977). "Two independent gas electron diffraction investigations of the structure of plumbous chloride". Journal of Molecular Structure. 42: 147–151. Bibcode:1977JMoSt..42..147H. doi:10.1016/0022-2860(77)87038-5.
  7. ^ CRC Handbook of Chemistry and Physics, 79th Edition, David R. Lide (Ed), p. 8-108
  8. ^ Brown, Lemay, Burnsten. Chemistry The Central Science. "Solubility-Product Constants for Compounds at 25 °C". (ed 6, 1994). p. 1017
  9. ^ Cotunnite
  10. ^ a b Dictionary of Inorganic and Organometallic Compounds. Lead(II) Chloride.http://www.chemnetbase.com]
  11. ^ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 365. ISBN 978-0-13-039913-7.
  12. ^ Lowack, R (1994). "Decasubstituted decaphenylmetallocenes". J. Organomet. Chem. 476: 25–32. doi:10.1016/0022-328X(94)84136-5.
  13. ^ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 524. ISBN 978-0-13-039913-7.
  14. ^ Aboujalil, Almaz; Deloume, Jean-Pierre; Chassagneux, Fernand; Scharff, Jean-Pierre; Durand, Bernard (1998). "Molten salt synthesis of the lead titanate PbTiO3, investigation of the reactivity of various titanium and lead salts with molten alkali-metal nitrites". Journal of Materials Chemistry. 8 (7): 1601. doi:10.1039/a800003d.
  15. ^ Stained Glass Terms and Definitions. aurene glass
  16. ^ Kirk-Othmer. Encyclopedia of Chemical Technology. (ed 4). p 913
  17. ^ Perry & Phillips. Handbook of Inorganic Compounds. (1995). p 213
  18. ^ Kirk-Othmer. Encyclopedia of Chemical Technology. (ed 4). p. 241

External linksEdit

  • IARC Monograph: "Lead and Lead Compounds"
  • IARC Monograph: "Inorganic and Organic Lead Compounds"
  • National Pollutant Inventory – Lead and Lead Compounds Fact Sheet
  • Case Studies in Environmental Medicine – Lead Toxicity
  • ToxFAQs: Lead