Which of the following complexes exhibits the highest paramagnetic behaviour? where gly = glycine, en = ethylenediamine and bpy = bipyridyl moieties (At no: $\text{Ti} = 22$, $\text{V} = 23$, $\text{Fe} = 26$, $\text{Co} = 27$)

Paramagnetic behaviour depends on the number of unpaired electrons ($n$). (A) In $[\text{V}(\text{gly})_2(\text{OH})_2(\text{NH}_3)_2]^+$, assuming gly is the glycinato ligand (charge $-1$) and $\text{OH}^-$ is hydroxo (charge $-1$), V is in the $+5$ oxidation state ($x - 2 - 2 + 0 = +1 \implies x = +5$). Thus, it has a $3d^0$ configuration ($n=0$). (B) In $[\text{Fe}(\text{en})(\text{bpy})(\text{NH}_3)_2]^{2+}$, Fe is in the $+2$ oxidation state with a $3d^6$ configuration. Since en, bpy, and $\text{NH}_3$ are strong field ligands, the complex is low-spin ($t_{2g}^6$) with $n=0$ (diamagnetic). (C) In $[\text{Co}(\text{ox})_2(\text{OH})_2]^-$ (intended as $[\text{Co}(\text{ox})_2(\text{OH})_2]^{3-}$ to account for the stable $+3$ state of Co), Co has a $3d^6$ configuration. Because $\text{OH}^-$ and $\text{ox}^{2-}$ act as weak field O-donor ligands in this context, it forms a high-spin complex with $n=4$ unpaired electrons. (D) In $[\text{Ti}(\text{NH}_3)_6]^{3+}$, Ti is in the $+3$ oxidation state with a $3d^1$ configuration ($n=1$). Since the cobalt complex has the maximum number of unpaired electrons ($n=4$), it exhibits the highest paramagnetic behaviour.