Mechanisms of the acid catalysed bridge cleavage reactions of two trinuclear ruthenium(III) complex ions [Ru-3(NH3)(13)(SCN)X-2](6+), (X = Cl-, Br-)

Acid catalysed bridge cleavage reaction of two doubly bridged trinuclear co mplex ions [Ru-3(NH3)(13)(SCN)X-2](6+), (X= Cl-, Br-) have been investigate d at 59 degrees in perchloric and nitric acid media respectively. Both the complexes show two stages of reaction. Plots of k(obs) versus [acid] are li near for both the complexes in the two stages of reactions. Only the plots for first stage have intercept on rate axis. The rate constants for the chl oro and the bromo complexes for acid - dependent path are as follows : firs t stage 5.15 x 10(-4) & 2.43 x 10(-4) dm(3) mol(-1) s(-1) and second stage 7.35 x 10(-3) & 4.02 x1 0(-4) dm(3) mol(-1)s(-1) respectively. An associati ve mechanism has been invoked for the reactions in which bond formation by the incoming solvent (water) molecule with the middle ruthenium atom leads to rupture of bridging bonds.