Lead(II) chloride

Lead(II) chloride
Names

The crystal structure of PbCl₂, in the unconventional crystallographic setting Pnam. This corresponds to the standard Pnma setting by switching the labels on the b and c axes.
IUPAC names Lead(II) chloride Lead dichloride
Other names Plumbous chloride Cotunnite Dichloroplumbylene
Identifiers
CAS Number	7758-95-4^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:88212^N
ChemSpider	22867^Y
ECHA InfoCard	100.028.950
EC Number	231-845-5
PubChem CID	166945
UNII	4IL61GN3YI^N
CompTox Dashboard (EPA)	DTXSID1041059
InChI InChI=1S/2ClH.Pb/h2*1H;/q;;+2/p-2^Y Key: HWSZZLVAJGOAAY-UHFFFAOYSA-L^Y
SMILES Cl[Pb]Cl
Properties
Chemical formula	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)
Solubility in water	0.99 g/100 mL (20 °C)^[1]
Solubility product (K_sp)	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 concentrated HCl (>6M)
Magnetic susceptibility (χ)	−73.8·10⁻⁶ cm³/mol
Refractive index (n_D)	2.199^[2]
Structure^[3]
Crystal structure	Orthorhombic, oP12
Space group	Pnma (No. 62)
Lattice constant	a = 762.040 pm, b = 453.420 pm, c = 904.520 pm
Formula units (Z)	4
Thermochemistry
Std molar entropy (S^⦵₂₉₈)	135.98 J K⁻¹ mol⁻¹
Std enthalpy of formation (Δ_fH^⦵₂₉₈)	-359.41 kJ/mol
Hazards^[5]
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H332, H351, H360, H372, H410
Precautionary statements	P201, P261, P273, P304+P340, P308+P313, P312, P391
NFPA 704 (fire diamond)	3 0 0
Lethal dose or concentration (LD, LC):
LD_Lo (lowest published)	140 mg/kg (guinea pig, oral)^[4]
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). N verify (what is ^YN ?) Infobox references

Chemical compound

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 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.^[6] PbCl₂ forms white orthorhombic needles.

Ball-and-stick model of part of the crystal structure of cotunnite
Space-filling model
Coordination geometry of Pb²⁺
Coordination geometry of Cl⁻
Coordination polyhedron of Pb²⁺

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.^[7] 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 K_sp = 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 K_sp = 1.8×10⁻¹⁰, copper(I) chloride (CuCl) with K_sp = 1.72×10⁻⁷ and mercury(I) chloride (Hg₂Cl₂) with K_sp = 1.3×10⁻¹⁸.^[8]^[9]

Synthesis

Solid lead(II) chloride precipitates upon addition of aqueous chloride sources (HCl, NaCl, KCl) to aqueous solutions of lead(II) compounds, such as lead(II) nitrate and lead(II) acetate:

Pb(NO₃)₂ + 2 HCl → PbCl₂(s) + 2 HNO₃

It also forms by treatment of basic lead(II) compounds such as Lead(II) oxide and lead(II) carbonate.

Lead dioxide is reduced by chloride as follows:

PbO₂ + 4 HCl → PbCl₂(s) + Cl₂ + 2 H₂O

It also formed by the oxidation of lead metal by copper(II) chloride:

Pb + CuCl₂ → PbCl₂ + Cu

Or most straightforwardly 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 PbCl_2(s).

PbCl_2(s) + Cl⁻ → [PbCl₃]⁻_(aq)

PbCl_2(s) + 2 Cl⁻ → [PbCl₄]²⁻_(aq)

PbCl₂ reacts with molten NaNO₂ to give PbO:

PbCl_2(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

Molten PbCl₂ is used in the synthesis of lead titanate and barium lead titanate ceramics by cation replacement reactions:^[13]
x PbCl_2(l) + BaTiO_3(s) → Ba_1−xPb_xTiO₃ + x BaCl₂
PbCl₂ is used in production of infrared transmitting glass,^[14] 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. There are now Bi, Pb, and Zn in the ore. At 500 °C, it receives treatment from Cl2 gas. First, ZnCl2 forms and is excreted. Pure Bi is left behind after PbCl2 forms and is eliminated. Lastly, BiCl3 would form.^[18]

Toxicity

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

References

^ NIST-data review 1980 Archived 2014-02-11 at the Wayback Machine
^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
^ Sass, Ronald L.; Brackett, E. B.; Brackett, T. E. (1963). "THE CRYSTAL STRUCTURE OF LEAD CHLORIDE". The Journal of Physical Chemistry. 67 (12). American Chemical Society (ACS): 2863–2864. doi:10.1021/j100806a517. ISSN 0022-3654.
^ "Lead compounds (as Pb)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ "Classifications - CL Inventory". echa.europa.eu.
^ Wells A. F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
^ 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.
^ CRC Handbook of Chemistry and Physics, 79th Edition, David R. Lide (Ed), p. 8-108
^ Brown, Lemay, Burnsten. Chemistry The Central Science. "Solubility-Product Constants for Compounds at 25 °C". (ed 6, 1994). p. 1017
^ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 365. ISBN 978-0-13-039913-7.
^ Lowack, R (1994). "Decasubstituted decaphenylmetallocenes". J. Organomet. Chem. 476: 25–32. doi:10.1016/0022-328X(94)84136-5.
^ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 524. ISBN 978-0-13-039913-7.
^ 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.
^ Dictionary of Inorganic and Organometallic Compounds. Lead(II) Chloride.[1]
^ Stained Glass Terms and Definitions. aurene glass
^ Kirk-Othmer. Encyclopedia of Chemical Technology. (ed 4). p 913
^ Perry & Phillips. Handbook of Inorganic Compounds. (1995). p 213
^ Kirk-Othmer. Encyclopedia of Chemical Technology. (ed 4). p. 241