Figure . Position of ligands in octahedral complex XII U5 Coordination XII U5 Coordination - - - - As the number of different ligands increases, the number of possible isomers also increases. For the octahedral complex of the type [MABCDEF] n± , where A, B, C, D, E and F are monodentate ligands, fifteen different orientation are possible corresponding to geometrical isomers. It is difficult to generate all the possible isomers.
Evaluate yourself : a . Three compounds A ,B and C have empirical formula CrCl .6H O. they are kept in a container with a dehydrating agent and they lost water and attaining constant weight as shown below. Identify the molecular formula of compounds.
Compound Initial weight of the compound(in g) Constant weight after dehydration (in g) . B . . C b .
Indicate the possible type of isomerism for the following complexes and draw their isomers (i) [Co(en) ][Cr(CN) ] (ii) [Co(NH ) (NO )] + (iii) [Pt(NH ) (NO )]Cl . . Optical Isomerism Coordination compounds which possess chairality exhibit optical isomerism similar to organic compounds. The pair of two optically active isomers which are mirror images of each other are called enantiomers.
Their solutions rotate the plane of the plane polarised light either clockwise or anticlockwise and the corresponding isomers are called 'd' (dextro rotatory) and 'l' (levo rotatory) forms respectively. The octahedral complexes of type [M(xx) ] n± , [M(xx) AB] n± and [M(xx) B ] n± exhibit optical isomerism. Examples: The optical isomers of [Co(en) ] + are shown in figure . .
[ ( ) ] + Co + Co + H2N-CH2-CH2-NH2 (en) Figure . - Optical isomer XII U5 Coordination XII U5 Coordination - - - - The coordination complex [CoCl (en) ] + has three isomers, two optically active cis forms and one optically inactive trans