9.5 Specify the oxidation numbers of the metals in the following coordination entities:

(i) [Co(H2O)(CN)(en)2]2+          

(ii) [CoBr2(en)2]+       

(iii) [PtCl4]2–                         

(iv) K3[Fe(CN)6]           

(v) [Cr(NH3)3Cl3]

 
(i) Co(H2O)(CN)(en)22+
Let the oxidation number of Co be x.
The charge on the complex is +2.
CoH2OCNen22+
x+0+-1+20=+2
x-1=2
x=+3
(ii) Pt(CI)42-
Let the oxidation number of Pt be x.
The charge on the complex is −2.
PtCl42-
x+4(1)=2x
x=+2
(iii)
 CoBr2en22+
x+2(-1)+2(0)=+1
x-2=+1
x=+3
(iv)   K3Fe(CN)6
i.e,
 FeCN63-
x+6(-1)=-3
x=+3
(v)
 CrNH33Cl3
x+3(0)+3(-1)=0
x-3=0
x=+3