Consider the complex given below ${\left[{\left({\mathrm{NH}}_3\right)}_5\stackrel{\mathrm{II}}{\mathrm{Ru}}\left({\mathrm{N}}_2\right)\stackrel{\mathrm{II}}{\mathrm{Ru}}{\left({\mathrm{NH}}_3\right)}_5\right]}^{4+}$and the statements regarding it.

(i) $\mathrm{N}-\mathrm{N}$ bond length is longer than that in free ${\mathrm{N}}_2$ molecule. 

(ii) It is diamagnetic having $t_2^4{e}_g^2$ configuration of each ${\mathrm{Ru}}^{2+}$ ion.

(iii) Back-bonding is involved in this.

The correct statement(s) is/are: