Question

[Ni(PPh$_3$)$_2$Cl$_2$] is a paramagnetic complex. Identify the {INCORRECT statements about this complex. A. The complex exhibits geometrical isomerism.
B. The complex is white in colour.
C. The calculated spin-only magnetic moment of the complex is $2.84$ BM.
D. The calculated CFSE (Crystal Field Stabilization Energy) of Ni in this complex is $-0.8\Delta_o$.
E. The geometrical arrangement of ligands in this complex is similar to that in Ni(CO)$_4$.
Choose the correct answer from the options given below:

• A. C, D and E only
• B. A and B only
• C. A, B and D only
• D. C and D only

Hint:

Ni(II) tetrahedral complexes are paramagnetic, coloured, and do not show geometrical isomerism.

Answer 1

The Correct Option is B

The given complex is: \[ [\text{Ni(PPh}_3)_2\text{Cl}_2] \]
Step 1: Oxidation state and electronic configuration.
Let oxidation state of Ni be $x$: \[ x + 2(0) + 2(-1) = 0 \Rightarrow x = +2 \] Thus, Ni$^{2+}$ has electronic configuration: \[ \text{Ni}^{2+}: 3d^8 \] Since the complex is paramagnetic, it must have unpaired electrons.

Step 2: Geometry of the complex.
Ni(II) with bulky ligands like PPh$_3$ forms a tetrahedral complex.
Tetrahedral complexes do not show geometrical isomerism.
Hence, \[ Statement A is incorrect. \]
Step 3: Colour of the complex.
Paramagnetic Ni(II) complexes are generally coloured due to $d$–$d$ transitions.
Thus, the statement that the complex is white is false.
Hence, \[ Statement B is incorrect. \]
Step 4: Magnetic moment.
For $d^8$ tetrahedral complex: \[ \text{Number of unpaired electrons} = 2 \] Spin-only magnetic moment: \[ \mu = \sqrt{n(n+2)} = \sqrt{2(4)} = \sqrt{8} \approx 2.83\ \text{BM} \] Thus, \[ Statement C is correct. \]
Step 5: CFSE calculation.
For tetrahedral $d^8$ configuration: \[ \text{CFSE} = -0.8\Delta_o \] Thus, \[ Statement D is correct. \]
Step 6: Comparison with Ni(CO)$_4$.
Ni(CO)$_4$ is a tetrahedral complex.
The given complex is also tetrahedral.
Hence, \[ Statement E is correct. \]
Step 7: Identify incorrect statements.
Incorrect statements are: \[ A and B \]
Final Answer: $\boxed{\text{A and B only}}$