What is oxidation state and coordination number of central metal ion in
(a) `(NH_(4))[CoF_(4)]` ?
(b) `[Pt(O_(2))(en)_(2)Br]^(+)`

Explanation

(a) `[overset(x-1)[CoF_(4))]^(2-)`, x-4=-2 or x=+2, Coordination no. =4.
(b) `O_(2)^(2-)` (peroxo) is monodentate, en is didentate and `Br^(-)` is monodentate. Hence, coordination no. =1+4+1=6.
`[overset(x)(Pt)(O_(2))^(2-)overset(0)((en))_(2)Br^(-)]^(+)`, x-2-1=+1 or x=4