Studies of ruthenium complexes, 8

The kinetics of the thermal substitution reaction of hexaamineruthenium (III) halides and cis-dihalogenotetraamineruthenium (III) halides have been studied in the solid state. The reaction rates and kinetic parameters were determined for these two reactions; [Ru(NH3)6]X3→[RuX(NH3)5]X2+NH3, (X=Br, I) and cis - [RuX2(NH3)4]X→[RuX3(NH3)3]+NH3, (X=Cl, Br). The values of the rate constant, the activation energy, and the activation entropy were 2.10x10-5 s-1 (at 1610C), 23.2 kcal mol-1, and -29.3 e.u. for the hexaamine bromide, and 2.92x10-5 s-1 (at 1620C), 31.3 kcal mol-1, and -10.1 e.u. for the cis-dibromotetraamine bromide. The Ssub(N)2 mechanism is more probable for the former reaction, while the Ssub(N)1 mechanism is more probable for the latter reaction. (author)