Synthesis and structure of technetium trichloride.

Technetium trichloride has been synthesized by reaction of Tc(2)(O(2)CCH(3))(4)Cl(2) with HCl(g) at 300 °C. The mechanism of formation mimics the one described earlier in the literature for rhenium. Tc(2)(O(2)CCH(3))(2)Cl(4) [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 Tc(3)Cl(9) 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 TcX(3) (X = Cl, Br) have confirmed the stability of TcCl(3) and suggest the existence of a polymorph of TcBr(3) with the ReBr(3) structure.