STUDIES ON THE BRIDGE CLEAVAGE REACTIONS OF DI-MU-HYDROXOTETRAKIS(BIGUANIDE)DICOBALT(III) ION IN THE PRESENCE OF PERCHLORIC AND NITRIC-ACIDS

Acid-catalysed bridge cleavage reaction of the compound [(BigH)(2) Co- mu(OH)(2)-Co(BigH)(2)](4+) has been investigated spectrophotometricall y with both perchloric and nitric acids in the temperature range 42 de grees-60 degrees. In acid medium, rupture of first bridge is rate dete rmining while breakage of the second bridge is fast. Bridge cleavage r eaction proceeds only through the acid-catalysed path. Rate equations, rate constants and activation parameters (Delta H double dagger, 44.3 +/-3.3 kJ mol(-1); Delta S double dagger, 188+/-18 JK(-1) mol(-1)) are similar in both the perchloric and the nitric acids.