[en] The process of the [Tc₂Cl₈]^3- claster anion formation has been studied by analyzing the stepwise syntheses. The initial compound is technecium (4) chlorine-containing complex (PyH)₂[TcCl₆]. The scheme is given of technecium (4) reduction with molecular hydrogen under pressure in solution of 11 N HCl. The [Tc₂Cl₈]^3- claster anion formation begins at 150 deg C. It has been confirmed spectrophotometrically that two forms of complexes are obtained in solid state at 150 deg C: hydrolyzed technecium (4) and claster. On the basis of the elemental analysis results the synthesized compound has a composition (PyH)₃[Tc₂Cl₈]x2H₂O