The complexes (NH3)4 CO*~(NH,.OH)*CO(NH,)~~+ and (NH3)4 Co~p(NH2,O,)*Co(NH,),*+ are relatively easy to prepare and can be used as starting material for the preparation of a wide range of dicobalt complexes. Details of the reactions of the p(NH,, OH) complex with HCI, HBr, HI. HNO,, H2S04, HCIO,. and HNO,, and of the p(NH,, 0,) complex with I-, NO2-, SO, ,and OH-are considered. The diaquo-complex (NH,),( H,O)Co.NH,-Co(H,O) (NH,),6+ can be prepared from the p(NH,, OH) complex and is a useful intermediate forthe preparation of nitrito-, fluoro-, and acetato-complexes. Details of spectra are given.