1. Why [Cu CI₄]^2- exist but [Cu I₄]^2- does not?
2. Show that all octahedral complexes of nickel [2]must have high spin?
3. Both[ Fe (CN)₆]^3- and [Fe (H₂O)₆]³⁺ are colourless in dilute solution .Why?

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Due to paucity of time it would not be possible for us to solve all your queries. We are providing solution to one of your queries. Try solving the rest of the questions yourself and if you face any difficulty then do get back to us.

1). Cu⁺² when reduced to Cu⁺ and Cu, it has standard electrode potential 0.16 V and 0.34 V respectively.
Cl₂ has an E⁰ of 1.36 V and I₂ has an E⁰ of 0.53 V which shows that iodine is less electronegative so the iodide anions would react with the cupric cations yielding iodine and either metallic copper or cuprous cations. Thus, the [CuI₄]^2- does not exists while [CuCl₄]^2- exists.