Technetium Tetrachloride Revisited: A Precursor to Lower-Valent Binary Technetium Chlorides

Technetium tetrachloride has been prepared from the reaction
of
technetium metal with excess chlorine in sealed Pyrex ampules at elevated
temperatures. The product was characterized by single-crystal and
powder X-ray diffraction, transmission electron microscopy, scanning
electron microscopy, and alternating-current magnetic susceptibility.
Solid TcCl4 behaves as a simple paramagnet from room temperature
down to 50 K with μeff = 3.76 μB. Below 25 K, TcCl4 exhibits an antiferromagnetic transition
with a Néel temperature (TN) of
∼24 K. The thermal behavior of TcCl4 was investigated
under vacuum at 450 °C; the compound decomposes stepwise to α-TcCl3 and TcCl2.