I have a 3-week lab experiment in my sophomore inorganic course that I call Project Werner, heavily adapted from Angelici's text, in which students first make their choice of 4 cobalt complexes: [Co(NH3)6]Cl3, [Co(NH3)5Cl]Cl2, [Co(NH3)4(CO3]NO3, or [Co(en)3]Cl3. In the second week, everyone carries out ligand substitution of [Co(NH3)5Cl]Cl2 to prepare the two linkage isomers of [Co(NH3)5(NO2)]Cl2. And week 3 is spent on characterization (UV-vis, IR, and solution conductivity).
Students love this lab, and after many years, I have all of the kinks worked out of it. My stash of cobalt complexes is slowly building up over time, and while they make a very nice display in the lab, I would like to find something useful to do with some of them. The stash of the chloro complex is very handy as it is the starting reagent for the nitrite substitution. But I am wondering if there is anything that I could do with the carbonato complex, [Co(NH3)4(CO3]NO3? Does anyone have any good ideas, or better yet, any preps?
Also, while reading through the wikipedia entry on linkage isomerism, I noticed that the thiocyanate isomers, [Co(NH3)5(SCN)]2+and [Co(NH3)5(NCS)]2+have very different colors. Does anyone have a prep for these? Are they easy to make? This might be a fun addition to the lab.