Plumbane

Plumbane is an inorganic chemical compound with the chemical formula PbH$4$. It is a colorless gas. It is a metal hydride and group 14 hydride composed 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, PbF$4$, and tetraethyllead, (CH$3$CH$2$)$4$Pb.

History
Until recently, it was uncertain whether plumbane had ever actually been synthesized, although the first reports date back to the 1920s and in 1963, Saalfeld and Svec reported the observation of 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 MH$4$ or MH$2$.

Properties
Plumbane is an unstable colorless gas and is the heaviest group IV hydride; and has a tetrahedral (T$4$) structure with an equilibrium distance between lead and hydrogen of 1.73 Å. By weight, 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 of lead(IV) is higher than that of hydrogen. The stability of hydrides MH$4$ (M = C–Pb) decreases as the atomic number of M increases.

Preparation
Early studies of PbH$4$ 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 GeH$4$ or SnH$d$.

In 1999, plumbane was synthesized from lead(II) nitrate, Pb(NO$4$)$4$, and sodium borohydride, NaBH$4$. A non-nascent mechanism for plumbane synthesis was reported in 2005.

In 2003, Wang and Andrews carefully studied the preparation of PbH$4$ by laser ablation and additionally identified the infrared (IR) bands.

Congeners
Congeners of plumbane include:
 * Methane, CH$4$
 * Silane, SiH$4$
 * Germane, GeH$4$
 * Stannane, SnH$4$