Plumbane
Encyclopedia
Plumbane, PbH4, is a metal hydride
Hydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...

 composed of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 and hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

. Plumbane is not well-characterized or well-known, and it is thermodynamically unstable with respect to the loss of a hydrogen atom. Derivatives of plumbane include lead tetrafluoride, PbF4 and tetraethyllead, (CH3CH2)4Pb.

History

Until recently, it was uncertain whether plumbane had ever actually been synthesized; although, in 1963, Saalfeld and Svec reported the observation of PbH4+ by mass spectrometry. Plumbane has repeatedly been the subject of Dirac–Hartree–Fock relativistic calculation
Relativistic quantum chemistry
Relativistic quantum chemistry invokes quantum chemical and relativistic mechanical arguments to explain elemental properties and structure, especially for heavy elements of the periodic table....

 studies, which investigate the stabilities, geometries, and relative energies of hydrides of the formula MH4 or MH2.

Properties

Plumbane is an unstable colorless gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

 and is the heaviest group IV hydride. Furthermore, plumbane has a tetrahedral (Td) structure with an equilibrium distance between Pb and hydrogen of 1.73 Å. By weight percent, the composition of plumbane is 1.91% hydrogen and 98.09% lead. In plumbane, the formal oxidation states of hydrogen and lead are +1 and -4, respectively, because the electronegativity
Electronegativity
Electronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...

 of lead is higher than that of hydrogen. The stability of metal hydrides with the formula MH4 (M = C-Pb) decreases as the atomic number of M increases.

Preparation

In general, metal hydrides are formed when hydrogen gas is allowed to react with metals. They can serve to store hydrogen gas, which is highly flammable.

Early studies of PbH4 revealed that the molecule is unstable as compared to its lighter congeners (silane
Silane
Silane is a toxic, extremely flammable chemical compound with chemical formula SiH4. In 1857, the German chemists and Friedrich Woehler discovered silane among the products formed by the action of hydrochloric acid on aluminum silicide, which they had previously prepared...

, germane
Germane
Germane is the chemical compound with the formula GeH4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is tetrahedral. It burns in air to produce GeO2 and...

, and stannane
Stannane
Stannane is the hydride of tin. Stannane can be prepared by the reaction of SnCl4 and LiAlH4. Stannane decomposes slowly at room temperature to give metallic tin and hydrogen and ignites on contact with air....

). It cannot be made by methods used to synthesize GeH4 or SnH4.

Recently, plumbane has been synthesized from lead(II) nitrate
Lead(II) nitrate
Lead nitrate is an inorganic compound with the chemical formula Pb2. It commonly occurs as a colourless crystal or white powder and, unlike most other lead salts, is soluble in water....

, Pb(NO3)2, and sodium borohydride
Sodium borohydride
Sodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are...

, NaBH4. Additionally, a non-nascent mechanism for plumbane synthesis has been developed.

In 2003, Wang and Andrews carefully studied the preparation of PbH4 by laser ablation
Laser ablation
Laser ablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma...

 and additionally identified the infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 (IR) bands.

Congeners

  • Methane
    Methane
    Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

     CH4
  • Silane
    Silane
    Silane is a toxic, extremely flammable chemical compound with chemical formula SiH4. In 1857, the German chemists and Friedrich Woehler discovered silane among the products formed by the action of hydrochloric acid on aluminum silicide, which they had previously prepared...

     SiH4
  • Germane
    Germane
    Germane is the chemical compound with the formula GeH4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is tetrahedral. It burns in air to produce GeO2 and...

     GeH4
  • Stannane
    Stannane
    Stannane is the hydride of tin. Stannane can be prepared by the reaction of SnCl4 and LiAlH4. Stannane decomposes slowly at room temperature to give metallic tin and hydrogen and ignites on contact with air....

    SnH4
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