In which of the following complexes the nickel metal is in highest oxidation state:

Options

A. `Ni(CO)_(4)`
B. `K_(2)NiF_(5)`
C. `[Ni(NH_(3))_(5)](BF_(4))_(2)`
D. `K_(4)[Ni(CN)_(6)]`

Answer

B

Explanation

Let x be the oxidation state of nickel then,
(1) `Ni(CO)_(4),x+4(0)=0 or x=0," " (2)[NiF_(6)]^(2-),x+6(-1)=-2 or x=+4,`
`(3) [Ni(NH_(3))_(6)]^(2+),x+4(0)=+2 or x=+2," " (4)[Ni(CN)_(6)]^(4-),x+6(-1)=-4 or x=+2`.