Lead(II) chloride

Lead(II) chloride
Names
IUPAC names
Lead(II) chloride
Lead dichloride
Other names
Plumbous chloride
Cotunnite
Identifiers
7758-95-4 YesY
ChEBI CHEBI:88212 YesY
ChemSpider 22867 YesY
Jmol interactive 3D Image
PubChem 166945
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)
10.8 g/L (20 °C)[1]
5.89×10−5 (20 °C)
Solubility slightly soluble in dilute HCl, ammonia;
insoluble in alcohol
2.199[2]
Structure
Orthorhombic, oP12
Pnma, No. 62
Thermochemistry
135.98 J K−1 mol−1
-359.41 kJ/mol
Hazards
Safety data sheet See: data page
Xn N
R-phrases R61, R20/22, R33, R62, R50/53
S-phrases S53, S45, S60, S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
0
3
0
Lethal dose or concentration (LD, LC):
1500 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
Refractive index (n),
Dielectric constant (εr), etc.
Thermodynamic
data
 Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
YesY verify (what is YesYN ?)
Infobox references

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.

Structure and properties

In solid PbCl2, each lead ion is coordinated by 9 chloride ions – 6 lie at the apices of a trigonal prism and 3 lie beyond the centers of each 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.[4] PbCl2 forms white orthorhombic needles. While Lead(II) chloride is abundant in many natural water reserves, it is unsafe for human consumption and must be filtered out.

Vaporized PbCl2 molecules have a bent structure with the Cl-Pb-Cl angle being 98° and each Pb-Cl bond distance being 2.44 Å.[5] Such PbCl2 is emitted from internal combustion engines that use ethylene chloride-tetraethyllead additives for antiknock purposes.

The solubility of PbCl2 in water is low (10.8 g/L at 20 °C) and for practical purposes it is considered insoluble. Its solubility product constant (Ksp) is 5.89×10−5. It is one of only four commonly insoluble chlorides, the other three being 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.[6][7]

Occurrence

Crystal structure of cotunnite, PbCl2

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.[8]

Synthesis

Lead(II) chloride precipitates from solution upon addition of chloride sources (HCl, NaCl, KCl) to aqueous solutions of lead(II) compounds such as Pb(NO3)2.

Pb(NO3)2(aq) + 2 NaCl(aq) → PbCl2(s) + 2 NaNO3(aq)
Pb(CH3COO)2(aq) + HCl(aq) → PbCl2(s) + 2 CH3COOH(aq)
basic PbCO3 + 2 HCl(aq) → PbCl2(s) + CO2(g) + H2O[9]
Pb(NO3)2(aq) + 2 HCl(aq) → PbCl2(s) + 2 HNO3(aq)

Treatment of lead dioxide with hydrochloric acid gives lead(II) chloride as well as chlorine gas:

PbO2(s) + 4 HCl → PbCl2(s) + Cl2 + 2 H2O

Treatment of lead oxide with hydrochloric acid gives lead(II) chloride as well as water

PbO(s) + 2 HCl → PbCl2(s) + H2O

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

Pb + Cl2 → PbCl2

Reactions

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.[10]

Lead(II) chloride is the main precursor for organometallic derivatives of lead, such as plumbocenes.[11] 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[12]

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.

Uses

xPbCl2(l) + BaTiO3(s) → Ba1-xPbxTiO3 + xBaCl2

Toxicity

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

References

  1. ↑ NIST-data review 1980
  2. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  3. ↑ "Lead compounds (as Pb)". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
  4. ↑ Wells A. F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  5. ↑ 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. doi:10.1016/0022-2860(77)87038-5.
  6. ↑ CRC Handbook of Chemistry and Physics, 79th Edition, David R. Lide (Ed), p. 8-108
  7. ↑ Brown, Lemay, Burnsten. Chemistry The Central Science. "Solubility-Product Constants for Compounds at 25 °C". (ed 6, 1994). p. 1017
  8. ↑ Cotunnite
  9. 1 2 Dictionary of Inorganic and Organometallic Compounds. Lead(II) Chloride.
  10. ↑ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 365. ISBN 978-0130399137.
  11. ↑ Lowack, R (1994). "Decasubstituted decaphenylmetallocenes". J. Organomet. Chem. 476: 25. doi:10.1016/0022-328X(94)84136-5.
  12. ↑ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 524. ISBN 978-0130399137.
  13. ↑ 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.
  14. ↑ Stained Glass Terms and Definitions. aurene glass
  15. ↑ Kirk-Othmer. Encyclopedia of Chemical Technology. (ed 4). p 913
  16. ↑ Perry & Phillips. Handbook of Inorganic Compounds. (1995). p 213
  17. ↑ Kirk-Othmer. Encyclopedia of Chemical Technology. (ed 4). p. 241

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