By making use of the trans-effect in platinum(II) complexes, show efficient routes for the synthesis of all the possible isomers of $\ce{[PtCl(NH3)2(py)]+}$ (where $\ce{py}$ = pyridine) from the starting material $\ce{K2PtCl4}$.
So far, I've had problems with trying to substitute ammonia and py in the right places. Since $\ce{Cl-}$ is higher on the trans effect list than the two ligands I want to substitute with, I found that it's just not possible to do that.