Identify the complexes which are expected to be coloured.
a. `[Ti(NO_(3))_(4)]` , b. `[Cu(NC CH_(3))_(4)]^(o+) BF_(4)^(ɵ)`
c. `[Cr(NH_(3))_(6)]^(3+)3Cl^(ɵ)` , d. `K_(3)[VF_(6)]`

Options

A. `[Ti(NO_(3))_(4)]`
B. `[Cu(NC CH_(3))_(4)]^(+)BF_(4)^(-)`
C. `[Cr(NH_(3))_(6)]^(3+)3Cl^(-)`
D. `K_(3)[VF_(6)]`

Answer

C, D

Explanation

Only those complexes are coloured in which the central metal ion has incompletely filled d-subshell.
`{:("Complex","Central ion","Outer metal ion configuration","Colour"),(Ti(NO_(3))_(4),Ti^(4+),3d^(0)4s^(0),"colourless"),([Cu(NC CH_(3))_(4)]^(+)BF_(4)^(-),Cu^(+),3d^(10)4s^(0),"colourless"),([Cr(NH_(3))_(6)]^(3+)3Cl^(-),Cr^(3+),3d^(3)4s^(0),"coloured"),(K_(3)[VF_(6)],V^(3+),3d^(2)4s^(0),"coloured"):}`