Synthesis and Structure of Technetium Trichloride

Technetium trichloride has been synthesized by reaction of Tc2(O2CCH3)4Cl2 with HCl(g) at 300 °C. The mechanism of formation mimics the one described earlier in the literature for rhenium. Tc2(O2CCH3)2Cl4 [P1̅; a = 6.0303(12) Å, b = 6.5098(13) Å, c = 8.3072(16) Å, α = 112.082(2)°, β = 96.667(3)°, γ = 108.792(3)°; Tc−Tc = 2.150(1) Å] is formed as an intermediate in the reaction at 100 °C. Technetium trichloride is formed above 250 °C and is isostructural with its rhenium homologue. The structure consists of Tc3Cl9 clusters [R3̅m; a = b = 10.1035(19) Å, c = 20.120(8) Å], and the Tc−Tc separation is 2.444(1) Å. Calculations on TcX3 (X = Cl, Br) have confirmed the stability of TcCl3 and suggest the existence of a polymorph of TcBr3 with the ReBr3 structure.