COBALT(III) COMPLEXES WITH 4-METHYLDIETHYLENETRIAMINE [2,2'-METHYLIMINODI(ETHYLAMINE)] - THEIR SEPARATION, CHARACTERIZATION AND REACTIONS

An efficient synthesis of 2, 2′-methyliminodi(ethylamine) trihydrochloride (medien, 3HC1) from diethylenetriamine (dien) is described. The reactions [Co(NH3)5C1] C12+ 2 medien, and oxygen-oxidation of cobalt(II) + 2 medien, with charcoal give only the s-fac isomer of [Co(medien)2]3 +. A little s-fac-[Co(dien)(medien)]3 + is also always formed, and this arises by demethylation of s-fac-[Co(medien)2]3+ with oxygen on charcoal. The substitution reaction [Co(NH3)5C1] C12 + 1 · 6 rnedien + 0 · 4 dien produces a complicated mixture of s-fac-[Co(medien)2]3+, all three isomers s-fac, u-fac and mer of [Co(dien)(medien)]3+, and all three isomers of [Co(dien)2]3+. A procedure using exchanges of the counter-ions, crystallization, and chromatography on SP-Sephadex cation-exchange resin is described for separating and isolating the products, and pure s-fac-[Co(dien)-(medien)] (C1O4)3 is obtained preparatively by this means. From isomerization of this complex in water the pure u-fac and mer [Co(dien)(medien)] 3 + isomers are isolated. 13C and 1H n.m.r. and visible spectra of the compounds are reported. The equilibrium isomer proportions of [Co(dien)2]3+, [Co(dien)(medien)] 3 + and [Co(medien)2]3+ are discussed. Some particular charcoal samples, which lack catalytic activity towards cobalt(III) equilibrations, effect the unusual conversion of s-fac-[Co(medien)2] 3 + into u-fac-[Co(amam)]3 + (amam = 2, 3-bis[(2-aminoethyl)(methyl)amino-ethylimino]-1-methylpiperazine). © 1979 Australian Journal of Chemistry. All rights reserved.