Hexaammine cobalt compounds

In their first publication on this subject,59 Werner and Miolati showed that the molecular conductances (fx) of coordination compounds decreased as successive molecules of ammonia were replaced by acid residues (negative groups or anions). For cobalt(III) salts, they found that fi for luteo salts (hexaammines) > fi for purpureo salts (acidopentaammines) > /t for praseo salts (di-acidotetraammines). The conductance fell almost to zero for the triacidotriammine Co(N02)3-(NH3)3 and then rose again for tetracidodiammines, in which the complex behaved as an anion. By such measurements, Werner and Miolati determined the number of ions in complexes of cobalt(III), platinum(II) and platinum(IV). They not only found support for the coordination theory, but they also elucidated the process of dissociation of salts in aqueous solution and followed the progress of aquations. 

The cobalt(II) reaction. The cobalt(II) reaction exhibited sigmoid nr-time curves giving values of between 170 and 230 kJ mol, except for the hexaammine compound in ammonia where was 132 kJ mol. The mechanism proposed is initially identical to that detailed above for the CoN reaction, but the divalent intermediate is suggested to be stabilized within a crystalline product ... 

Tanaka et al. [76] have studied the decompositions of various solid hexaammine, halopentaammine and oxalatoammine cobalt(in) compounds. Kinetic data for these reactions A and EJ were determined from changes in the concentrations of Co with time, and values of were found to parallel the magnitudes of the orbital energies of the compounds. 

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