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Nickel(II) has a coordination number of 4. When excess KCN is added to NiCl2, a cyano complex A is formed. When excess KCl is added to NiCl2, a chloro complex B is formed. What are the hybridisations of the metal centre in A and B respectively?
- dsp², sp³
- sp³, sp³
- dsp², dsp²
- sp³d², d²sp³
Correct answer: dsp², sp³
Solution
CN- is a strong-field ligand that forces pairing of the d⁸ electrons in Ni²+, giving a square-planar [Ni(CN)4]²- complex with dsp² hybridisation. Cl- is a weak-field ligand that does not cause pairing, so [NiCl4]²- is tetrahedral with sp³ hybridisation.
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