Number of unpaired electron \(=5\)
So, \(Mn\) must be in \(+2\) oxidation state \(\left( Mn ^{+2}\right)\)
\(\Rightarrow 2+(-6)=-x\)
\(\Rightarrow-4=-x\)
\(\Rightarrow x=4\)
$(I)\,[Cr(NO_3)_3(NH_3)_3]$ $(II)\, K_3[Fe(C_2O_4)_3]$ $(III)\,[CoCl_2(en)_2]^+$ $(IV)\, [CoBrCl(ox)_2]^{3-}$