Synthesis
A tube, dried by fanning with a flame and prepared for evacuation
and melt-sealing, is charged with a small amount of Nbl5 under
completely anhydrous conditions. The tube is then sealed in a high vacuum and the end containing
Nbl5 is heated to 270°Cwhile the reactor is in a horizontal position.
The liberated iodine collects at the other end, which is kept at a
temperature of about 35°C (p[I
2] = 0.8 mm.). The reaction time is
about 48 hours. A residue of Nbl4 remains on the spot where the
starting Nbl
5
was placed; it can be sublimed at about 300 °C under
the above-indicated I
2 pressure.
Nbl
5= Nbl
4 +
1/
2
I
2.
