The octahedral diamagnetic low spin complex among the following is:
\( [\mathrm{Co}(\mathrm{NH}_3)_6]^{3+} \)
\( [\mathrm{CoCl}_6]^{3-} \)
\( [\mathrm{CoF}_6]^{3-} \)
\( [\mathrm{NiCl}_4]^{2-} \)