PbF₄, PbCl₄ exist but PbBr₄ and PbI₄ do not exist because of 

F and Cl are more oxidising in nature and can achieve Pb in (IV) O.S. but Br₂ and I₂ can not achieve Pb in (IV) O.S. secondly ${\mathrm{Pb}}^{4+}$ is strong in oxidising nature and in its presence, Br^- and I^- can not exist.