The set of molecules in which the central atom is not obeying the octet rule is

The octet rule was given by Lewis. It states that elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.

Among the given options ${\mathrm{SF}}_6(12 \mathrm{e}), {\mathrm{PCl}}_5\left(10\mathrm{e}\right), {\mathrm{XeF}}_2(10 \mathrm{e})$ does not follow octet rule. As we can see that in none of them, the central atom has 8 electrons in its valence shell. They are also called expended octet.