Among $\mathrm{Co}^{3+}, \mathrm{Ti}^{2+}, \mathrm{V}^{2+}$ and $\mathrm{Cr}^{2+}$ ions, one if used as a reagent cannot liberate $\mathrm{H}_2$ from dilute mineral acid solution, its spin-only magnetic moment in gaseous state is $\_\_\_\_$ B.M. (Nearest integer)
