In ${\mathrm{SiF}}_6^{2-}$ and ${\mathrm{SiCl}}_6^{2-}$ which one is known and why

In ${\mathrm{SiF}}_6^{2-}$ and ${\mathrm{SiCl}}_6^{2-}$, ${\mathrm{SiF}}_6^{2-}$ is known due to the small size of F atoms. The small six F atoms can be easily accommodated around Si atom to form ${\mathrm{SiF}}_6^{2-}$ while in ${\mathrm{SiCl}}_6^{2-}$, six large CI atoms cannot be accommodated around Si atom.