$(1)$ $\left[{Co}({en})\left({NH}_{3}\right)_{4}\right] {Cl}_{2}$ $\quad\quad\quad1$ chelate ring
$(2)$ $\left[{Co}({en})_{3}\right] {Cl}_{2}$ $\quad\quad\quad\quad\quad\quad3$ chelate ring
$(3)$ $\left[{Co}({en})_{2}\left({NH}_{3}\right)_{2}\right] {Cl}_{2}$ $\quad\quad\quad2$ chelate ring
$(4)$ $\left[{Co}\left({NH}_{3}\right)_{6}\right] {Cl}_{2} \quad\quad\quad\quad\quad0$ chelate ring
${\left[ Ni ( CN )_4\right]^{2-},\left[ Ni ( CO )_4\right],\left[ NiCl _4\right]^{2-}}$
${\left[ Fe ( CN )_6\right]^{4-},\left[ Cu \left( NH _3\right)_4\right]^{2+}}$
${\left[ Fe ( CN )_6\right]^{3-} \text { and }\left[ Fe \left( H_2O\right)_6\right]^{2+}}$
($R $ = alkyl group; $en$ = ethylenediamine)