Lead(II) chloride

Lead(II) chloride
IUPAC name

Lead(II) chloride
Lead dichloride
Other names

Plumbous chloride
Cotunnite
Identifiers
CAS number 7758-95-4 Y
PubChem 166945
ChemSpider 22867 Y
Jmol-3D images Image 1
Properties
Molecular formula PbCl2
Molar mass 278.10 g/mol
Appearance white odorless solid
Density 5.85 g/cm3
Melting point

501 °C
Boiling point

950 °C
Solubility in water 6.73 g/L (0 °C)
9.9 g/L (20 °C)
33.4 g/L (100 °C)
Solubility product, Ksp 1.7×10−5
Solubility slightly soluble in dilute HCl, ammonia;
insoluble in alcohol
Refractive index (nD) 2.199[1]
Structure
Crystal structure Orthorhombic, oP12
Space group Pnma, No. 62
Thermochemistry
Std enthalpy of
formation ΔfHo298		 -359.41 kJ/mol
Standard molar
entropy So298		 135.98 J K−1 mol−1
Hazards
MSDS External MSDS
EU Index 082-001-00-6
EU classification Repr. Cat. 1/3
Harmful (Xn)
Dangerous for the environment (N)
R-phrases R61, R20/22, R33, R62, R50/53
S-phrases S53, S45, S60, S61
NFPA 704
0
3
0
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
Structure and
properties		 n, εr, etc.
Thermodynamic
data		 Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.

Contents

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.[2] PbCl2 forms white orthorhombic needles.

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.[3] 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 (9.9 g/L at 20 °C) and for practical purposes it is considered insoluble. Its solubility product constant (Ksp) is 1.7×10−5. 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.[4][5]

Occurrence

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. The composition is 74.50% Pb and 25.50% Cl. Cotunnite occurs near volcanoes: Vesuvius, Italy; Tarapacá, Chile; and Tolbachik, Russia.[6]


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[7]
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.[8]

Lead(II) chloride is the main precursor for organometallic derivatives of lead, such as plumbocenes.[9] 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[10]

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

Uses

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

Toxicity

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

References

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

External links