On the question of metallic "poly(carbon diselenide)"

In 1982, we found that when carbon diselenide in organic solvents such as methylene chloride or dioxane was pressurized at about 5 Kbar and heated at 100°C for several hours, a black solid was obtained in >95% yield. The solid was amorphous and electrically insulating (<10^-12 S cm^-1), but when this compound was heated at 160 °C it was transferred to a different material which was found to be a semiconductor (10^-3 S cm^-1). In a series of recent papers, Kobayashi and coworkers have reported the synthesis of a metallic crystalline poly(carbon diselenide) via the pressurization and annealing of pure liquid CSe₂ instead of its solution. Using a variety of techniques, we find that the metallic poly(carbon diselenide) synthesized is a mixture of an amorphous CSe polymeric material and trigonal selenium. Percolation of the CSe polymer probably provides the observed metallic conductivity of the material ({A figure is presented}. The relationship between structure and electrical properties of poly(carbon diselenide) prepared under various conditions is discussed.