Write the IUPAC names of the following coordination compounds (any three):

(a) $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_4 \mathrm{Cl}\left(\mathrm{NO}_2\right)\right] \mathrm{Cl}$

(b) $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_2$

(c) $\mathrm{K}_3\left[\mathrm{Cr}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]$

(d) $\left[\mathrm{Co}(\mathrm{en})_2 \mathrm{Br}_2\right]^{+}$

(a) On the basic of crystal field theory write the electronic configuration for $$\mathrm{d}^5$$ ion with a strong field ligand for which $$\Delta_0>\mathrm{P}$$.

(b) $$\left[\mathrm{Ni}(\mathrm{CO})_4\right]$$ has tetrahedral geometry while $$\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$$ has square planar yet both exhibit diamagnetism. Explain.

[Atomic number : $$\mathrm{Ni}=28$$ ]