Question

How many complexes among the following are paramagnetic

$\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{3-}\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\left[\mathrm{Co}(\mathrm{en})_{3}\right]^{3+}$ $\left[\mathrm{V}(\mathrm{CO})_{6}\right],\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}\left[\mathrm{Ni}(\mathrm{dmg})_{2}\right]$ $\left[\mathrm{Pt}(\mathrm{Cl})_{2}\left(\mathrm{NH}_{3}\right)_{2}\right]\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}\left[\mathrm{Cu}(\mathrm{CN})_{4}\right]^{3-}$

Answer 1

$\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{3-},\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+},\left[\mathrm{V}(\mathrm{CO})_{6}\right],\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+},\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}$
are paramagnetic due to the presence of unpaired electrons.