Question

What is the coordination number of cobalt in [Co(en)(H₂O)(Br)(Cl₂)]?

Answer 1

The coordination number of cobalt in the complex [Co(en)(H₂O)(Br)(Cl₂)] is 6. This is because the ethylenediamine (en) ligand is bidentate and donates two lone pairs through its two nitrogen atoms. The water molecule H₂O, bromide ion Br⁻, and each of the two chloride ions Cl⁻ are monodentate, each donating one lone pair.

Coordination number is en = 2, H₂O = 1, Br⁻ = 1, 2Cl⁻ = 2

Total coordination number = 2 + 1 + 1 + 2

= 6

∴ The coordination number of cobalt in this complex is 6.