Why PbI4 does not exit?

PbI4 does not exist because lead (Pb) typically has a +2 oxidation state in its compounds, forming stable compounds like PbI2. In PbI4, lead would need to assume a +4 oxidation state; however, this state is less stable due to the inert pair effect, where the s-electrons of lead are less likely to participate in bonding. Additionally, the larger iodine atoms create steric hindrance that destabilizes a +4 lead compound. As a result, PbI4 is not a viable compound under normal conditions.