Co-Ordination Compounds Question 157
Question: Nickel (Z = 28) combines with a uninegative monodentate ligand $ {X^{-}} $ to form a paramagnetic complex $ {{[NiX_4]}^{2-}} $ . The number of unpaired electron(s) in the nickel and geometry of the complex ion are, respectively:
Options:
A) One, tetrahedral
B) Two, tetrahedral
C) One, square planar
D) Two, square planar
Show Answer
Answer:
Correct Answer: B
Solution:
If $ {X^{-}} $ is weak field ligand (say $ C{l^{-}} $ ), then $ {{[NiCl_4]}^{2-}} $ is tetrahedral $ (sp^{3}) $ with two unpaired electrons.
If $ {X^{-}} $ is strong field ligand (say $ C{N^{-}} $ ), then $ {{[Ni{{(CN)}_4}]}^{2-}} $ is square planar $ (dsp^{2}) $ with no unpaired electrons.
Also given $ {{[NiX_4]}^{2-}} $ is paramagnetic, so $ {X^{-}} $ is weak ligand.
