Molar mass 137.65 g/mol Appearance black powder | Density 7.2 g/cm³ | |
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Nickel selenide is the inorganic compound with the formula NiSe. As for many metal chalcogenides, the phase diagram for nickel selenide is complicated. Two other selenides of nickel are known, NiSe2 with a pyrite structure, and Ni2Se3. Additionally, NiSe is usually nonstoichiometric and is often described with the formula Ni1−xSe, with 0 < x <0.15. These materials are all black semi-conducting solids when obtained as fine powders and silvery materials when obtained as larger crystals. The nickel selenides are insoluble in all solvents but can be degraded by strongly oxidizing acids.
Synthesis and structure
Typically NiSe is prepared by high temperature reaction of the elements. Such reactions typically afford mixed phase products. Milder methods have also been described using more specialised techniques such as reactions of the elements in liquid ammonia in a pressure vessel.
Like many related materials, nickel selenide adopts the nickel arsenide motif. In this structure, nickel is octahedral and the selenides are in trigonal prismatic sites.