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Linkage Isomers: Synthesis and Characterization of [Co(NH3)5ONO]Cl2 and [Co(NH3)5NO2]Cl2
Divalent cobalt is more stable than trivalent cobalt for simple salts of cobalt, with only a few salts ofCo(III) known (e.g. CoF3). Formation of a coordination complex stabilizes a higher oxidation state as evidenced by a number of octahedrally coordinated complexes. In this experiment, you will prepare twolinkage isomer compounds, [Co(NH3)5ONO]Cl2and [Co(NH3)5NO2]Cl2. 1) The synthesis of [Co(NH3)4CO3]NO3 involves the following unbalanced equation, Co(NO3)2 + NH3(aq) + (NH4)2CO3 + H2O2 →[Co(NH3)4CO3]NO3 + NH4NO3 + H2O Cobalt nitrate [Co(NO3)2] is deliquescent (tends to absorb atmospheric water vapor and become liquid). Upon exposure to atmospheric moisture, cobalt nitrate has the formulaCo(NO3)2▪6H2O. Co(II) complexes react very rapidly by ligand exchange, thus a possible first step in the reaction: Co(OH2)62+ + 4NH3(aq) + CO32- → Co(NH3)4CO3 + 6H2O Which could then be oxidized by addition ofH2O2 to form [Co(NH3)4CO3]+. 2) One synthesis scheme of [Co(NH3)5Cl]Cl2 involves the following equations, [Co(NH3)4CO3]+ + 2HCl → [Co(NH3)4(OH2)Cl]2+ + CO2(g) + Cl[Co(NH3)4(OH2)Cl]2+ + NH3(aq) →[Co(NH3)5(OH2)]3+ + Cl[Co(NH3)5(OH2)]3+ + 3HCl → [Co(NH3)5Cl]Cl2(s) + H2O + 3H+

[Adapted From: Tanaka, J. and Suib, S.L.. “Experimental Methods in Inorganic Chemistry”; Prentice-Hall: 1999 and Jolly,W.L. “The Synthesis and Characterization of Inorganic Compounds” Prentice-Hal: 1970.]


3) Synthesis of [Co(NH3)5ONO]Cl2 and [Co(NH3)5NO2]Cl2 involves the following: [Co(NH3)5Cl]2+ + H2O[Co(NH3)5H2O]3+ + NO2[Co(NH3)5ONO]2+ Synthesis and Experimental Procedure: Chloropentaamminecobalt(III) chloride, [Co(NH3)5Cl]Cl2 Make a solution of 5.0 g ammonium chloride NH4Cl in 30 mL of concentratedaqueous ammonia in a 250 mL Erlenmeyer flask. While stirring with magnetic stirbar, slowly add 10 g of cobalt(II) chloride hexahydrate. While continuously stirring, slowly add 8 mL of a 30% H2O2...
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