$(A)$ $\left[ Ni \left( H _{2} O \right)_{2}( en )_{2}\right]^{2+}$
$(B)$ $\left[ Ni \left( H _{2} O \right)_{4}(\text { en })\right]^{2+}$ અને
$(C)$ $\left[ Ni ( en )_{3}\right]^{2+}$
| ઉદીપક | પ્રક્રિયા |
| $(A)$ $TiCl_4$ | $(i)$ Wacker process |
| $(B)$ $PdCl_2$ | $(ii)$ Ziegler - Natta polymerization |
| $(C)$ $CuCl_2$ | $(iii)$ Contact process |
| $(D)$ $V_2O_5$ | $(iv)$ Deacon's process |