Uranium borohydride

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Uranium borohydride
Image:Uranium borohydride.jpg
Properties
Molecular formula U(BH4)4
Molar mass 297.27 g/mol
Solubility in other solvents Decomposes
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Uranium borohydride U(BH4)4 is a volatile uranium compound with boron. It is a tetrahedral monomer in its gas phase and has a vapor pressure of 4 mmHg at 60 °C.

During the Manhattan Project the need arose to find volatile compounds of uranium suitable for use in the diffusion separation of the uranium isotopes. Uranium borohydride is, after uranium hexafluoride, the most volatile compound of uranium known. Uranium hexafluoride presented serious handling difficulties, which required the directors of this effort to seek alternatives. When the synthesis problems had been sufficiently well defined it was decided to see what kinds of other difficulties might arise in the use of a boron compound for uranium separation. Enrico Fermi's purported comment when he observed the neutron cross section for boron—"My God! It's as big as the side of a barn!"—not only gave a name to the unit of cross section (barns), it also put an end to thoughts of using uranium borohydride for the diffusion process.

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