Q. Describe Coordinated octahedral complexes?

Six-coordinated octahedral complexes of the type Mubr, Ma₃b₃, Ma₃b₂c, Ma₃bcd,  Ma₂bcd, Ma₂bcde, Mabcd of would all give geometrical isomers. Systems with one or two bidentate ligands and rest monodentate would also give geometrical isomers. Thus we-see that with this geometry a large number of isomers are possible whether they can be isolated or separated is a different question which depends on so many factors. As we increase the number of different ligands, the possible number of isomers increases. For example, Mub₂

type of complex would give only two isomers cis- and trans-. Similarly for Ma3b3 type of complex we again get two isomers facial (fac-) and meridional (mer-) isomers. In the   former (fac-) three ligands of one type form one triangular face of the octahedron and the other three on the opposite face, Fig. (a). In  the latter (mer-). one set of these ligands art  arranged around an edge of the octahedron whereas the other set occupies the opposite edge  as shown in Fig.(b).