Draw the structures of geometrical isomers of the following coordination complexes:
[Co(NH3)3Cl3] and [CoCl2(en)2+]
(en = ethylene diamine and atomic number of Co is 27).
Coordination isomerism: This type of isomerism occurs in compounds containing both cationic and anionic complexes and isomers differ in the distribution of ligands in the coordination sphere of cationic and anionic parts. The examples are:
(i) [Co(NH3)6] [Cr(CN)6] and [Cr(CNH3)6] [Co(CN)6]
(ii)[Cu(NH3)4] [PtCl4] and [Pt(NH3)4] [CuCl4]
This type of isomerism is also shown by compounds in which the metal ion is the same in both cationic and anionic complexes. For example:
(a) [Cr(NH3)6] [Cr(CN)6] and [Cr(NH3)2(CN)4][Cr(NH3)2(CN)4]
(b) [Pt(NH3)4] [PtCl4] and [PtCl(NH3)3] [PtCl3(NH3)]
(i) Explain geometrical isomerism with reference to square planar complexes giving one example. How is tetrahedral complexes with simple ligands do not exhibit geometrical isomerism?
(ii) Using valence bond theory, predict the shape and magnetism (paramagnetism) or diamagnetism of [Co(CO)4]– (at. no. of Co = 27)?
(iii) How is stability of coordination compounds determined in aqueous solution?