Technetium trichloride has been synthesized by reaction of Tc-2(O2CCH3)(4)Cl-2 with HCl(g) at 300 degrees C. The mechanism of formation mimics the one described earlier in the literature for rhenium. Tc-2(O2CCH3)(2)Cl-4 [P (1) over bar; a = 6.0303(12) angstrom, b = 6.5098(13) angstrom, c = 8.3072(16) angstrom, alpha = 112.082(2)degrees, beta = 96.667(3)degrees, gamma = 108.792(3)degrees; Tc-Tc = 2.150(1) angstrom] is formed as an intermediate in the reaction at 100 C. Technetium trichloride is formed above 250 degrees C and is isostructural with its rhenium homologue. The structure consists of Tc3Cl9 clusters [R (3) over barm; a = b = 10.1035(19) angstrom, c = 20.120(8) angstrom] and the Tc-Tc separation is 2.444(1) angstrom. 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.