Formation of the intermediate, aquohydroxobis (ethylenediamine)cobalt(III) complex, in the preparation of cis-bromoamminebis (ethylenediamine)cobalt(III) bromide by the reaction of bis[bis(ethylenediamine)cobalt(III)-μ-dihydroxo]diaquocobalt(II) sulfate with ammonium bromide in water

The production of cis-[CoBr(NH3)(en)(2)]Br-2 by reaction of [Co(H2O)(2){(OH)(2)Co(en)(2)}(2)](SO4)(2) with ammonium bromide in water was investigated. The reaction seems to proceed through the intermediate, [Co(H2O)(OH)(en)(2)](2+), and then convert to the product, cis-[CoBr(NH3)(en)(2)](2+) This is supported by the observation that the absorption spectrum of the reaction solution immediately after the disappearance of the starting complex was different from that of cis[CoBr(NH3)(en)(2)](2+) but was quite similar to that of [Co(H2O)(OH)(en)(2)](2+). In order to confirm this reaction pathway, cis-[Co(H2O)(OH)(en)(2)]Br-2 was prepared and reacted with ammonium bromide producing the expected complex, cis-[CoBr(NH3)(en)(2)]Br-2.