NIOBIUM(V) IODIDE

Химические свойства

black powder(s); monoclinic, a=1.058 nm, b=0.658nm, c=1.388nm; sensitive to moisture; obtained by reaction of excess I2 with Nb metal in a sealed tube [STR93] [KIR81]

Подготовка

A vertical tube of Vycor or Pyrex glass (I.D. approximately 23 mm., wall thickness 2.5 mm.) is charged with 4-12 g. of Nb metal (either solid or powder). A dense glass wool plug is placed over the charge and approximately 20 cm. from the closed tube end, followed by a 20% excess of pure, resublimed I₂ powder. The tube and its contents are thoroughly degassed in a high vacuum and melt-sealed under vacuum. Then the reactor is placed in a slightly inclined position (with the Nb metal at the higher and the I₃ at the lower end) and heated by means of two separate tubular electric furnaces (these meet at the center of the tube). The niobium is heated to 300℃ and the I₂ first to 180℃ and then to 250℃. The reaction is nearly quantitative after 10-15 hours and Nbl₅ crystals collect in the transition zone between the two temperature regions. The yields are lower with Nb powder than with solid Nb. The reactor is broken at the center, the Nbl₅ is removed under anhydrous conditions, and repeatedly rinsed with dry petroleum ether (under N₂) until the adhering I₂ is removed and the petroleum ether stays colorless. The traces of petroleum ether are evaporated in vacuum.