  Heavy transition metal magnets with $J_{\rm eff}$ $=$ 1/2 electronic ground
states have attracted recent interest due to their penchant for hosting new
classes of quantum spin liquids and superconductors. Unfortunately, model
systems with ideal $J_{\rm eff}$ $=$ 1/2 states are scarce due to the
importance of non-cubic local distortions in most candidate materials. In this
work, we identify a family of iridium halide systems [i.e. K$_2$IrCl$_6$,
K$_2$IrBr$_6$, (NH$_4$)$_2$IrCl$_6$, and Na$_2$IrCl$_6 \cdotp $ 6(H$_2$O)] with
Ir$^{4+}$ electronic ground states in extremely close proximity to the ideal
$J_{\rm eff}$ $=$ 1/2 limit, despite a variation in the low-temperature global
crystal structures. We also find ordered magnetic ground states for the three
anhydrous systems, with single crystal neutron diffraction on K$_2$IrBr$_6$
revealing Type-I antiferromagnetism. This spin configuration is consistent with
expectations for significant Kitaev exchange in a face-centered-cubic magnet.
