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Maggie Geselbracht, Reed College
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Joined: 11/17/2007 - 11:00am

Werner cobalt complexes

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.

Cheers,
Maggie

Kyle Grice, DePaul University
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Joined: 07/22/2010 - 5:29pm

There's plenty of things you could try with [Co(NH3)4(CO3]NO3. How about use them to make Co3O4 nanoparticles?

http://www.sciencedirect.com/science/article/pii/S0925838811022225

That'd be a cool thing to incorporate into an inorganic lab, if you have one of the techniques they use to characterize the products.

 

Here's a review on the linkage isomerism of the SCN complex and an original paper on the isomerization (using dilute acid, althogh you would want to substitute HBF4 or something else for HClO4... I am not a fan of perchlorates). You should be able to find the preps there.

http://www.sciencedirect.com/science/article/pii/0010854594800782

http://pubs.acs.org/doi/abs/10.1021/ic50085a044

 

Cheers,

Kyle

Postdoctoral Scholar, UCSD

soon to be Assistant Professor, DePaul University