Question

A nickel complex NiR4 C 2 has an absorption spectrum with peaks that have ɛ values of around 150. R and Cl occupy similar positions in the spectrochemical series. Are the chlorines coordinated? The questions is from Physical Methods for Chemists 2nd Ed. by Drago Chapter 10 question 3.

Answer 1

Ni contains greater number of d electrons, that is, 8 therefore, it shows lower coordination number, that is, 4 and exists in either square planar or tetrahedral geometry depending upon the ligand. In the given complex Ni must be coordinated with four R groups either in square planar or tetrahedral geometry and having oxidation state +2. Therefore, 2 chloride ions must be present outside the coordination sphere to balance the two positive charge on the complex. Hence, the Ni must not be coorinated with chloride ion.