  Discovery of new transition metal compounds with large spin orbit coupling
(SOC) coexisting with strong electron-electron correlation among the $d$
electrons is essential for understanding the physics that emerges from the
interplay of these two effects. In this study, we predict a novel class of
$J_{eff}=1/2$ Mott insulators in a family of fluoride compounds that are
previously synthesized, but not characterized extensively. First principles
calculations in the level of all electron Density Functional Theory + Dynamical
Mean Field Theory (DFT+DMFT) indicate that these compounds have large Mott gaps
and some of them exhibit unprecedented proximity to the ideal, $SU(2)$
symmetric $J_{eff}=1/2$ limit.
