  Motivated by the newly-discovered intercalated iron chalcogenide
superconductors, we construct a single orbital tight-binding model for
topological insulators on the square lattice with a perfect vacancy
superstructure. We find that such lattice structure naturally accommodates a
non-vanishing geometry phase associated with the next-nearest-neighbor
spin-orbit interaction. By calculating the bulk band structures and the finite
stripe edge states, we show that the topological insulator phases can be tuned
at certain electron fillings in a wide range of the model parameters. The
possible implications of these results for the iron deficient compounds
$(A,Tl)_{y}Fe_{2-x}Se_2$ have been discussed.

Strongly Correlated Electrons;Superconductivity