Characterisation of the Mixed Ligand Complexes

The usual spectroscopic techniques ir, visible/uv and reflectance spectroscopy can be used for characterisation. Measurement of the molar electrical conductivity of solutions and comparing with solutions of simple salts can be used to establish the charges in the ionic components of die complexes. In the case of the chloro-, nitrito and carbonate-complexes, measurements of conductivity and recording of spectra should be done on freshly prepared solutions. KBr discs are preferably used for recording infiared spectra. 

Place a suitable sample of the freshly prepared nitrito-complex in an oven at 150 C. At intervals say, 20, 40, 70, 110 minutes, take a small amount and run an ir spectrum and quickly prepare a 0.01 M solution and run die visible electronic spectrum between 400-750 nm. Compare these with the freshly prepared compound and with the spectra of the nitro-compound. Draw your conclusions. 

Chelating diamines eg diaminoethane (en) or diaminopropane (pn) form complexes when mixed with cobalt(II) salts in presence of an oxidant. Mixed ligand complexes may be also prepared in presence of a second ligand. 

1 Preparation and analysts of Irans-dichlorobis (diaminoethane) cobaltflll) chloride 

Mix 12 cm of 1,2-diaminoethane with 120 cm of water and add this to a solution of 32 g of cobalt(II) chloride hexahydrate in 100 cm of water. Cautiously add 40 cm of freshly dispensed 50 volume hydrogen peroxide. Then add 40 cm of 1 1 cone. HCl/water and evaporate until a surface crust forms. Cool the container and filter off the crystals under suction. Wash on the filter with ethanol and then with ether (no flames ). 

---