Cobalt pentammine complexes

J. Sand and 0. Genssler15 obtained a series of complex salts by the action of nitric oxide on ammoniaeal soln. of cobalt salts. They considered the products to be formed by the addition of two mols. of the cobalt pentammines. Thus, cobalt nitrosylpentamminodichloride, [Co(N0)(NH3)5]C12, furnishes black crystals supposed to be constituted Cl2[(NH3)5Co.NO.NO.Co(NH3)5]C12 or [Co2(N2O2)(NH3)10]C14. 

Induced electron transfer has been investigated in the action of one-electron oxidants on pyridinemethanolpentammine-cobalt(iii) complexes. The direct [and silver(i)- and cobalt(ii)-catalysed] oxidations of pentammine-(pyridine-4-methanol)cobalt(iii) (G) and the corresponding pyridine-3-methanol complex by cerium(iv) yield aldehydic complexes of cobalt(iii)... 

Cobalt can also be separated from nickel in alkaline conditions, by first adding ammonia and H2O2 to form cobalt(III) pentammine complex, at ambient temperature and pressure ... 

A considerable amount of controversy appears to exist in the literature (1) regarding the mechanism of base hydrolysis of acido-pentammine-cobalt(III) complexes. Detailed investigations on the kinetics of base hydrolysis of several complexes of this type, [Co(NHj) X] , where X = Cl , Br" or N , have been reported by earlier investigators (2-4). It is known (5) that in [Co(NH ) (S20 )] the thiosulphate is so firmly bound that on treating with potassium cyanide all the ammonia are displaced leading to the formation of [Co(CN)g(S20 )l ". 

C3 KINETICS AND MECHANISM OF NUCLEOPHILIC SUBSTITUTION IN AN ACIDO-PENTAMMINE-COBALT(III) COMPLEX IN AQUEOUS SOLUTION, D. Banerjea and T.P. Das Gupta... 

As with rhodium (and cobalt), introduction of five ammonia molecules is relatively straightforward, but the sixth substitution is difficult, requiring more forcing conditions. One versatile route involves the formation of the pentammine triflate complex ion [Ir(NH3)5(03SCF3)]2+, where the labile triflate group is readily replaced by water, then by a range of anionic ligands [148]. 

Ammonia forms complex derivatives with all three classes of iridium compounds. When added to iridious chloride, IrCl2, or to iridic chloride, IrCl4, the complex salts formed are analogous to the series of platinous and platinic ammine derivatives. When ammonia is added to the trichloride, many complex derivatives are formed which are similar to rhodic, cobaltic, and chromic compounds. For example, when ammonia acts upon ammonium iridiochloride a compound is produced having the formula [Cl(NHj)5lr]Cl2, and called chloro-pentammine-iridium dichloride. 

Reductions of monosubstituted iron(iii) complexes have been studied, the reactions being inner sphere with rates in the order Br > Cl > F" in contrast to the corresponding europium(ii) systems. The order does, however, parallel that for the Cr reduction of pentammine-cobalt(m) halide complexes. Reactions with platinum(iv) complexes have been studied, and in the case of [Pt(NH3)sa] + and [Pt(NH3)sOH] + a two-electron change is involved with intermediate formation of Cr and subsequent production of dimeric Cr" complexes ... 

Electron-transfer reactions between Co-complexes and reductants are being studied in this laboratory. As was noted by Gould [17] earlier, who studied electron-transfer reactions between pentammine cobalt complexes and Cr(II), the main factor in determining the acceleration is the valencies of the oxidants and reductants, as shown... 

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