
%0 Journal Article
%A House, DA 
%A Maclagan, RGAR 
%T Anionopentaaminecobalt(III) complexes with polyamine ligands. XIX. Computer simulated intermediates for dissociative aquation reactions
%J Australian Journal of Chemistry
%D 1984/02/01
%V 37
%N 2
%P 239-248
%K 
%R https://doi.org/10.1071/CH9840239
%U https://www.publish.csiro.au/paper/CH9840239 
%X Strain energy minimization calculations have been performed for several octahedral chloropenta-amine cobalt(III) complexes with polyamine ligands. Similar calculations on the five-coordinate residue obtained by removal of the chloro ligand allow an estimation of the geometry and energy of a potential intermediate in a chloride release reaction proceeding via a dissociative mechanism. In all cases the five-coordinate residue is less strained than the six-coordinate octahedron and the non-replaced ligands play an essential role in determining the resulting distortion. Thus for the series mer-CoCl(NN)(dien)2+ (NN = en, (NH3)2,tn), the total strain energy difference between the minimized ground state and the minimized five-coordinate residue is 12.2, 18.3 and 25.8 kJ mol-1, respectively. This order is identical (where data are available) to that of the rate constants (and activation energies) for thermal aquation, Hg2+ assisted aquation and mer &#8594; fac-dien isomerization in this series. Similar calculations have been performed for a series of trans-CoCl2(N4)+ systems and again the energy differences are in the approximate order of the rates of thermal aquation. In the case of N4 = (NH3)2, the energy difference between trans-and cis-CoCl(NH3)4(OH2)2+ products is about 1 kJ mol-1, the trans-isomer being the more stable. 
