  We study the phase diagram of a square lattice Hubbard model with a perfect
vacancy superstructure. The model can be also defined on a new bipartite
lattice with each building blocks consisting of a minimal square. The
non-interacting model is exactly solved and a mid-band gap opens at the Fermi
energy in the weak inter-block hopping regime. Increasing the Coulomb
interaction will develop the N\'eel antiferromagnetic order with varying block
spin moments. The metal-insulator transition with $U_{\rm MI}$ smaller than the
one without vacancies occurs above the magnetic instability $U_{\rm M}$. The
emergent intermediate magnetic metal phase develops substantially in the
moderate inter-block hopping regime. Drastic increases in the ordered moment
and gap magnitude on the verge of non-interacting band insulator signal a
possible distinction between the magnetic semi-conductor and the
Mott-insulator. The implications of these results for the recent discovered
(A,Tl)$_{y}$Fe$_{2-x}$Se$_2$ compounds are discussed.
