Question

The oxidation number of cobalt in K[Co(CO)₄] is

(i) +1

(ii) +3

(iii) −1

(iv) −3

Answer 1

We know that CO is a neutral ligand and K carries a charge of +1.

Therefore, the complex can be written as K⁺[Co(CO)₄]⁻. Therefore, the oxidation number of Co in the given complex is −1. Hence, option (iii) is correct.