Anionopentaaminecobalt(III) Complexes With Polyamine Ligands. XXVI. Spontaneous and Hg²⁺-Assisted Chloride Release Kinetics From Some CoCl(tacn)(diamine)²⁺ Complexes

Abstract

The rate of spontaneous ( k_H ) and Hg²⁺ assisted ( k_Hg ) chloride release from some CoCl ( tacn )( diamine )²⁺ complexes [ tacn = 1,4,7-triazacyclononane; diamine = ethane-1,2-diamine (en), propane-1,3-diamine ( tn ), 2-aminomethylpyridine ( ampy )] have been measured in acidic aqueous solution as a function of temperature and pressure. Rate constants (at 25.0°C), ΔH^‡ (kJ mol^-1), ΔS^‡ (J K^-1 mol^-1), ΔV^‡ (cm³ mol^-1) are: 10⁶ k_H (en) = 1.63 (s^-1), 93, -44, -3.6; 10⁶k_H ( tn ) = 1.86 (s^-1), 92, -47, -4.5; 10⁶k_H ( ampy ) = 0.343 (s^-1), 103, -22; 10³k_Hg (en) = 11.0 (dm³ mol^-1 s-1), 74, -32, +1.44; 10³k_Hg ( tn ) = 54.0 (dm³ mol-¹ s-¹), 77, -13, +3.26; 103k_Hg ( ampy ) = 10.2 (dm³ mol^-1 s^-1), 76, -30, +0.86. The normal accelatory influence observed when en is replaced by tn is very weak in these structurally rigid tacn systems.