Question

Which of the following is more likely to be colourless? 1. [Co(H2O)6]2+ 2.[Mn(CN)6]3- 3.[CrCl3(H2O)3] 4.[Ag(NH3)2]+

Answer 1

in the complex [Ag(NH3)2]+ the oxidation number of Ag is +1
i.e. electric config. of Ag+ is [Kr] 4$d^{10}$
this is why there are no scope for d-d transition, so colourless.
but in other cases there are partially filled d orbital present. so, d-d transition is possible in other cases.