In which of the following complexes is the oxidation state of the metal zero?

The formula of the complex $Tris(ethylenediamine)cobalt(III)$ sulphate is:

What is the oxidation number of iron in the compound $[Fe(H_2O)_5(NO)]SO_4$?

The oxidation state and coordination number of $Cr$ in $K_3[Cr(C_2O_4)_3]$ are respectively:

The $IUPAC$ name of $Na_3[Co(ONO)_6]$ is .....

Write the $IUPAC$ names of the following coordination compounds:
$(i)$ $[Co(NH_3)_6]Cl_3$
$(ii)$ $[Co(NH_3)_5Cl]Cl_2$
$(iii)$ $K_3[Fe(CN)_6]$
$(iv)$ $K_3[Fe(C_2O_4)_3]$
$(v)$ $K_2[PdCl_4]$
$(vi)$ $[Pt(NH_3)_2Cl(NH_2CH_3)]Cl$