Substitution reactions of rutbenium(ll) complexes containing heterocyclic ligands: Aquation of bis-bipyridine-dil 1, 2, 4-triazolejrutheniumtll) in perchloric acid

Abstract

Aquation of [Ru(bipy)₂(Htrz)₂]²⁺, (where Htrz= 1, 2, 4-triazole, a heterocyclic ligand) in the presence of perchloric acid (0.05-1.0 mol dm^-3) has been investigated spectrophotometrically between 21° to 40°C. The reaction proceeds in stages with the formation of monoaqua and diaqua products which subsequently undergoes a redox reaction to give ruthenium(m) and other products. Activation parameters are: <img src='/image/spc_char/delta.gif' border=0><i>H</i>^≠ 64 ± 4, 64 ± 3 and 73 ± 4 kJ mol^-1 and <img src='/image/spc_char/delta.gif' border=0><i>S</i>^≠ - 94 ± 8, - 102 ± 8 and - 76 ± 10 JK^-1 mol^-1 respectively for the first step and acid-free and acid-catalysed paths of the second step. Compared to chloride complex the triazole complex is more inert due to its higher enthalpy of reaction and bonding properties. Aquation of the complex shows appreciable associative character.