Synthesis and Structure of Technetium Trichloride

摘要

Technetium trichloride has been synthesized by reaction of Tc_2(O_2CCH_3)_4Cl_2 with HCI(g) at 300 ℃. The mechanism of formation mimics the one described earlier in the literature for rhenium. Tc_2(O_2CCH_3)_2Cl_4 [PI; a = 6.0303(12) ?, b = 6.5098(13) ?, c = 8.3072(16) ?, a = 112.082(2)°, β = 96.667(3)°, γ = 108.792(3)°; Tc-Tc = 2.150(1) ?] is formed as an intermediate in the reaction at 100 ℃. Technetium trichloride is formed above 250 ℃ and is isostructural with its rhenium homologue. The structure consists of Tc_3Cl_9 clusters [R3m; a = b= 10.1035(19) ?, c = 20.120(8) A], and the Tc-Tc separation is 2.444(1) ?. 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.