Plumbane

Plumbane

Plumbane, PbH4, is a metal hydride comprised of lead and hydrogen. 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 tetra-ethyl lead, (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 studies, which investigate the stabilities, geometries, and relative energies of hydrides of the formula MH4 or MH2.

Properties

Plumbane is an unstable colorless gas and is the heaviest group IV hydride. Furthermore, plumbane has a tetrahedral (Td) structure with an equilibrium bond distance 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. The stability of metal hydrides with the formula MH4 (M = Si-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, germane, and stannane). It cannot be made by methods used to synthesize GeH4 or SnH4.

Recently, plumbane has been synthesized from lead(II) nitrate, Pb(NO3)2, and sodium borohydride, NaBH4. Additionally, a non-nascent mechanism for plumbane synthesis has been developed.

In 2002, Wang, X. et al. carefully studied the preparation of PbH4 by laser ablation and additionally identified the infrared (IR) bands.

Congeners

References

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