Question

11. An octahedral complex [MA6]3+ is red, and a related complex [MB6]3+ is green (A and B = neutral monodentate ligands).

a) Which ligand, A or B, generates the greater crystal field splitting and why?

b) Which complex would you expect to be more readily oxidized and why?

c) Would you expect a colour change to orange-yellow or blue when the metal is reduced from [MA6]3+ to [MA6]2+?

My thoughts are that the first complex absorbs green and the 2nd complex absorbs red so the 2nd complex so the energy gap for the 1st complex has higher, Is this right?

Answer 1

9 [ Col₆]³⁺ => Red => higher energy => green

[ Col¹₆]³⁺ => green => absorved Lower energy => Red

*
=> absorbs higher energy Radiation [CONH₃)₆]⁺

[CO(NH₃)₆]³⁺ => higher energy green because NH3 is strong field liqand energy gap more then complex  

[CO(H₂O)₆]³⁺  becaues H₂O is weak field liqand energy gap less then

[CO(NH₃)₆]³⁺ complex.

[M A 6]³⁺ Reduction [M A ₆ ]²⁺

the colour change orange yellow or blue b/c the metal ion converted in +3 oxidation state to +2 oxidation state because NH₃ from high spin complex with 3d. Series transition element in +2 .O .S