Cobalt 1,2-ethanediamine -, trans

CljCoN C His, Cobalt(III), dichloro-bis(l,2,-ethanediamine)-, trans-, chloride, 29 167... 

BrCoN40,S2C4H,g H O, Cobalt(III), aqua-bromobis(l, 2-ethanediamine)-, dithio-nate, trans-, monohydrate, 21 124 Brp2NS, Imidosulfurous difluoride, bromo-, 24 20... 

A large majority of diacidobis(l, 2-ethanediamine)cobalt(III) complexes can be synthesized from the (carbonato)bis(l, 2-ethanediamine)cobalt(III) ion. This is now readily available in high yield and purity.1 cis- and trans-Dichlorobis(l, 2-ethanediamine)cobalt(III) chlorides are obtained from the carbonato complex with hydrochloric acid using appropriate conditions. These isomeric dichloro salts are widely used starting materials for further syntheses. In this respect, the analogous dibromo complexes can be more convenient starting materials because bromide is substituted from the cobalt center more readily than is chloride ion. The milder conditions minimize the production of cobalt(II), a common side reaction. 

Werner prepared cis- and tazns-dibromobis(l, 2-ethanediamine)cobalt(III) bromide by reacting the carbonato bromide with concentrated hydrobromic acid.2 In the cold, the cis isomer resulted the trans isomer was obtained by heating the mixture. The reaction proceeds via ds-aquabromobis(l, 2-ethanedi-amine)cobalt(III) dibromide which can be isolated by this route. In our hands, the preparations, as originally described, are not reproducible. The reaction times and yields are variable, depending too critically on the conditions for one not intuitively skilled in the art to consistently obtain the desired cis or trans form. However, the syntheses described here for the cis and trans dibromo complexes and based on this reaction are reproducible if one adheres closely to the procedures. 

Other preparative methods have been reported.2,3 ds-Dibromobis(l, 2-ethane-diamine)cobalt(III) bromide is obtained in reasonable yield by evaporating a neutral aqueous solution of the trans isomer to dryness. The reaction between ds-diazidob is( 1,2-ethanediamine)cobalt(III) perchlorate and hydrobromic acid proceeds rapidly and quantitatively at ambient temperature, largely with retention of the cis configuration to yield the dibromo bromide.4,s The diazido starting complex6 7 can be made within 1 hour in greater than 90% yield. 

In addition to the cis and trans dibromo complexes, the syntheses of c/s-aqua-bromobis(l,2-ethanediamine)cobalt(III) dibromide monohydrate and trans-aquabromobis(l,2-ethanediamine)cobalt(III) dithionate monohydrate are described. It is of historical interest that of the hundreds of cis/trans isomeric pairs of diacidobis(l,2-ethanediamine)cobalt(III) complexes known to Werner,3 the trans isomers in the classical aquahalo series eluded him. The procedures described here for their isolation are a modification of much later works, 8 in which the more soluble trans complexes were obtained pure as their sulfate salts by fractional crystallization of cis/trans mixtures. The syntheses of cis-[Co(en)2(OH2)Cl]S04-2H201-9 and ds-[Co(en)2(0H2)Cl]Br2"H209 are described in previous volumes of this series. The preparation of frans-aquachloro-bis(l, 2-ethanediamine)cobalt(III) dithionate monohydrate is given here to complete the series. 

C1CoN407S2C4H,8 HjO, Cobalt(HI), aquachlo-robis( 1,2-ethanediamine)-, dithionate, trans-, monohydrate, 21 125 ClF8nCl2H2, Thallium(III), chlorobis(2,3,4,6-tetrafluorophenyl-), chlorobis(2,3,5,6-tetra-fluorophenyl)-, 21 73... 

The title complex (as the chloride) was first reported by Kyuno and Bailar,1 who obtained cis-a and m-(i isomers by the ligand displacement reaction of cis-a-dichloro(N,N -bis(2-aminoethyl)-l,2-ethanediamine)cobalt(lll) chloride in gaseous and liquid ammonia. However, its trans isomers were not prepared until 1980.2... 

Br3CoN4C4H16, Cobalt(lll), dibromobis( 1,2-ethanediamine)-, bromide, trans-,... 

N2C2HJ, 1,2-Ethanediamine, chromium complex, resolution of, 26 24, 27, 28 cobalt complex, 29 167 platinum complexes, 27 314, 315 ruthenium complex, 29 164 N2CeH,4, 1,2-Cyclohexanediamine, cir-, trans-(R,R)-, and trans-(S,S)-, platinum complex, 27 283 N2CjH,j, 1,2-Ethanediamine,... 

---