${\left[ Ni ( CN )_4\right]^{2-},\left[ Ni ( CO )_4\right],\left[ NiCl _4\right]^{2-}}$
${\left[ Fe ( CN )_6\right]^{4-},\left[ Cu \left( NH _3\right)_4\right]^{2+}}$
${\left[ Fe ( CN )_6\right]^{3-} \text { and }\left[ Fe \left( H_2O\right)_6\right]^{2+}}$