In which of the following compounds transition metal is in zero oxidation state ?

[Co(NH3)6]Cl3  X + 6(0) = +3X = +3Ox.state of cobalt is +3[Fe(H2O)5 NO]SO4 [Fe(H2O)5 NO]+2X + 5(0) + 1 = +2X = +1In this complex called browning complex,Ox.state of Iron is +1Co2(CO)82X + 8(0) = 0X = 0Oxidation state of Iron is zeroK3[Fe(CN)6] [Fe(CN)6]-3X + 6(-1) = -3X = +3OX.state Iron is +3