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 ( kH ) and Hg2+ assisted ( kHg ) 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 kH (en) = 1.63 (s-1), 93, -44, -3.6; 106kH ( tn ) = 1.86 (s-1), 92, -47, -4.5; 106kH ( ampy ) = 0.343 (s-1), 103, -22; 103kHg (en) = 11.0 (dm3 mol-1 s-1), 74, -32, +1.44; 103kHg ( tn ) = 54.0 (dm3 mol-1 s-1), 77, -13, +3.26; 103kHg ( 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.