\(\mathrm{Co}^{+3}=3 \mathrm{d}^{6} 4 \mathrm{s}^{0} 4 \mathrm{p}^{0}\)
\(\because\) in presence of strong field ligand, pairing of electrons occurs so in this complex no unpaired electron is present and
it is low spin complex.
$(I)\, [Ni(CN)_4]^{2-}\,\,\,(II)\, [NiCl_4]^{2-}\,\,\,(III)\,Ni(CO_4)\,\,\,$
$(IV)\, [Ni(H_2O)_6 ]^{2+}$