Methods of thermogravimetry, infrared spectroscopy, electron absorption spectra and magnetic moment measurings were used to a study thermal solid-phase behaviour of onium hexachlororuthenates (4) of (AH)/sub 2/(RuCl/sub 6/) and (A'H/sub 2/)(RuCl/sub 6/) type, where A-benzimidazole (BAZ), pyridine (py), ammonia, A'-phenanthroline-ortho (o-phen), ethylenediamine (en). It was established that heating of solid (BAZH)/sub 2/(RuCl/sub 6/)x2H/sub 2/O and (o-phen H/sub 2/)(RuCl/sub 6/)xH/sub 2/O in 20-500 deg C range leads to separation of crystallization water and the following extraction of hydrogen chloride with formation of cis-(Ru(BAZ)/sub 2/Cl/sub 4/) and (Ru(o-phen)Cl/sub 4/). (pyH)/sub 2/(RuCl/sub 6/) heating causes initially the separation of two moles of hydrogen chloride with formation of cis-(Ru(py)/sub 2/Cl/sub 4/); further increase of temperature leads to reduction separation of chloride with formation of (Ru(py)/sub 2/Cl/sub 3/)/sub 2/ dimer. The mixture of ruthernium chlorides is prepared under conditions of isothermal heating of (NH/sub 4/)/sub 2/(RuCl/sub 6/) and (enH/sub 2/)(RuCl/sub 6/) compounds at temperatures close to the beginning of their decomposition. The separation of intermediate ruthenium compounds of diamine type with ammonia and ethylendiamine failed.