One isomer of [PdBr₂(NH₃)₂] is unstable with respect to a second isomer, and the isomerization process can be followed by IR spectroscopy. The IR spectrum of the first isomer shows absorptions at 480 and 460 cm⁻¹ assigned to n(PdN) modes. During isomerization, the band at 460 cm⁻¹ gradually disappears and that at 480 cm⁻¹ shifts to 490 cm⁻¹. Rationalize these data.