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 TcCl(4) behaves as a simple paramagnet from room temperature down to 50 K with μ(eff) = 3.76 μ(B). Below 25 K, TcCl(4) exhibits an antiferromagnetic transition with a Néel temperature (T(N)) of ∼24 K. The thermal behavior of TcCl(4) was investigated under vacuum at 450 °C; the compound decomposes stepwise to α-TcCl(3) and TcCl(2).