Aqueous solution of nickel sulphate on treating with pyridine and then adding a solution of sodium nitrite gives dark blue crystals of :

Options

A. `[Ni(py)_(4)]SO_(4)`
B. `[Ni(py)_(2)(NO_(2))_(2)]`
C. `[Ni(py)_(4)](NO_(2))_(2)`
D. `[Ni(py)_(3)(NO_(2))]_(2)SO_(4)`

Answer

C

Explanation

`[Ni(H_(2)O)_(4)]SO_(4)`+Pyridine +`NaNO_(2)to [Ni(Py)_(4)](NO_(2))_(2)`
Stronger ligand, pyridine displaces weaker ligand, `H_(2)O` in aqueous solution.
`[Ni(py)_(4)](NO_(2))_(2)` is formed as dark blue crystals on crystallisation.