Preparation and crystallographic properties of the trichlorides, tribromides, and tri-iodides of uranium, neptunium, and plutonium

Abstract

The preparation of uranium and neptunium trihalides has been investigated. Reduction of the appropriate tetrahalide by zinc at ca. 600 °C provides a safe, reliable route to UCl₃, UBr₃, UI₃, NpCl₃, and NpBr₃. This reaction is superior to reduction by aluminium metal. Direct union of the elements at 500 °C yields NpI₃ with no evidence for the formation of NpI₄. The new trivalent oxyhalides NpOCl, NpOBr, and NpOI have been identified crystallographically as by-products of certain reactions. Unit-cell dimensions are reported for these trihalides and oxyhalides, and for PuBr₃ and PuI₃.