Dichlorobis l,2-ethanediamine cobalt III Chloride

Checked by STANLEY KIRSCHNER,f THADDEUS J. GISH.f and STEVEN BARBERt 

4-traws-[Co(en)2(N02)2]N03 + 16HC1 + SCHzO + 4(NH2)2CO - 4-trans-[Co(en)2Cl2]ClHCl-2H20 + 6N2 + 9C02 + IIH2O 

The synthesis employs unrecrystallized trans-[Co(en)2(N02)2]N03, obtained in 90% yield within 2.5 h from basic reagents. The product, washed with methanol and then ether and air-dried, is sufficiently pure for the next step. 

Urea is well known as a scavenging reagent for HNO2, and in the following modified synthesis it may be included to reduce toxic fumes (NO2)  

I In that preparation it is advisable to dilute each of the 1,2-ethanediamine and nitric acid with twice its mass of ice prior to their careful mixing. 

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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. 

Irans-Dichlorobis(l,2-ethanediamine)cobalt(III) chloride is prepared from [Co(en)2(C03)]Cl (150 g) and concentrated hydrochloric acid (400 mL), as described for the dibromo analog in Section 28-B. Oven drying (100°,2 hours) yields 143 g (92%). The material is recrystallized from a filtered, saturated aqueous solution by adding an equal volume of methanol and then diluting carefully with a 10-fold volume excess of acetone. After 1 hour at 5°, the fine grass-green needles are collected, washed with two portions each of acetone and then diethyl ether, and air dried. Recovery is nearly quantitative. fra s-Dichlorobis(l,2-ethanediamine)cobalt(lH) chloride (11.4 g, 40mmole) is... 

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