Question

Our sample was made of NiSO₄ ∙ 6H₂O and NH₃ and ethanol. We did 2 trials one tiration with NaOH and another with EDTA solution.

After the NH3 molecules acted as Bronsted bases in the reaction with aqueous HCl they became NH4 + cations. Explain why NH3 can function as a ligand with Ni2+ while NH4 + cannot function as a ligand with Ni2+. Use structures to illustrate your answers.

Thank you.

Answer 1

We know to behave as a ligand the molecule should have atleast a lone pair of electron.

So now when we look at ammonia (NH₃) we see that it has 1 lone pair of electron which it can donate to central metal ion (Ni+2) . Hence it can behave as a ligand

In case of NH₄⁺ we see that the lone pair of electron is lost as the NH₃ is ionised to NH₄⁺ . So due to absence of lone pair , the NH4+ cannot donate electrons to central atom . Hence cannot act as ligand .