Which compound is zero valent metal complex

Options

(a) [Cu(NH₃)₄]SO₄
(b) [Pt(NH₃)₂Cl₂]
(c) [Ni(CO)₄]
(d) K₃[Fe(CN)₆]

Correct Answer:

[Ni(CO)₄]

Explanation:

[Cu(NH₃)₄]SO₄ → oxidation number of Cu = +2. [Pt(NH₃)₂Cl₂] → Oxidation number of Pt = +2. [Ni(CO)₄] → oxidation number of Ni = 0. K₃[Fe(CN)₆] → oxidation number of Fe = +3.