Question

Identify the type of isomerism represented in each pair of images. Explain your answer and be specific. (4 pts) . a. Ci NH3 b. The tetrahedral, high-spin, tetrachlorochromate (!I) complex [CrCl.]2- absorbs light with a wavelength of 605 nm. a. Draw the electron configuration that the chromium center in this complex would adopt (3 pts) Calculate the energy gap in the d orbitals of the chromium ion in kJ/mol. (2 pts) b.

Answer 1

1)

a) In one isomer, all three ligands are on the same side or "face" of the octahedral while in the other has only two ligands of any type on the same face. In other words, isomer on the left has all three similar ligands with bond angles 90 degrees relative to each other while the one on the right has relative angles 90-90-180 degrees. This type of isomerism is an off-shoot of the cis-trans-isomerism, but exclusive to octahedral complexes and is called the Mer-Fac isomerism or Meridional-Facial Isomerism. The isomer on the left with all similar ligands on the same face is the Facial isomer while the other isomer on the right is the Meridional isomer since all three ligands of the same type are lying on the same molecular plane.

b) The only variation among these two isomers is difference in the coordination of an amine group in the thiourea derivative on the right of the metal ion. While one ligand has the methyl substituted amine nitrogen bonded coordinately to the metal ion, the other has the N-phenyl nitrogen atom coordinately linked to the ion. Therefore, these are linkage isomers.