$\mathrm{EAN}=\mathrm{Z}-\mathrm{O} \cdot \mathrm{N} \cdot+2(\mathrm{C} \cdot \mathrm{N} \cdot)$
$=26-0+2(5)$
$=26+10$
$=36$
only one central metal atom/lon is present and it follows $EAN$ rule, so it is mononuclear

$(i)\ XeF_4\ (ii)\ SF_4\ (iii)\ [Ni (Cl_4)]^{2-}\ (iv)\ [ptCl_4]^{2-}$