Question 12 Marks
a. On the basis of crystal field theory, write the electronic configuration for $d ^4$ with a strong field ligand for which $\Delta_0>P$.
b. A solution of $\left[ Ni \left( H _2 O \right)_6\right]^{2+}$ is green but a solution of $\left[ Ni ( CO )_4\right]$ is colourless. Explain.
[Atomic number : $Ni =28$ ]
b. A solution of $\left[ Ni \left( H _2 O \right)_6\right]^{2+}$ is green but a solution of $\left[ Ni ( CO )_4\right]$ is colourless. Explain.
[Atomic number : $Ni =28$ ]
Answer
View full question & answer→a. If $\Delta_0> P$, then on the basis of crystal field theory the electronic configuration of the $d ^4$ ion will be $t _{2 g}^4 e _g^0$ as it is associated with strong field and low spin situation.
b. $H _2 O$ is a weak field ligand in $\left[ Ni \left( H _2 O \right)_6\right]^{2+}$. As a result, $Ni ^{2+}$ has unpaired electrons. In this compound, $d$-electrons from the lower energy level can be stimulated to the higher energy level, implying that a d-d transition is possible. As a result, $\left[ Ni \left( H _2 O \right)_6\right]^{2+}$ appears green, whereas $\left[ Ni ( CO )_4\right]$ is colourless due to the absence of an unpaired electron in the complex. CO is a strong field ligand that produces electron pairing.
b. $H _2 O$ is a weak field ligand in $\left[ Ni \left( H _2 O \right)_6\right]^{2+}$. As a result, $Ni ^{2+}$ has unpaired electrons. In this compound, $d$-electrons from the lower energy level can be stimulated to the higher energy level, implying that a d-d transition is possible. As a result, $\left[ Ni \left( H _2 O \right)_6\right]^{2+}$ appears green, whereas $\left[ Ni ( CO )_4\right]$ is colourless due to the absence of an unpaired electron in the complex. CO is a strong field ligand that produces electron pairing.
