Chapter 9, Problem 9D.4E

(a)

Interpretation Introduction

Interpretation:

The orbital energy level diagram and the number of unpaired electrons in ${\left[\text{Zn}{\left({\text{OH}}_{\text{2}}\right)}_{\text{6}}\right]}^{\text{2+}}$ complex have to be given.

Answer to Problem 9D.4E

There is no unpaired electron in ${\left[\text{Zn}{\left({\text{OH}}_{\text{2}}\right)}_{\text{6}}\right]}^{\text{2+}}$ complex.

Explanation of Solution

The oxidation number of zinc in ${\left[\text{Zn}{\left({\text{OH}}_{\text{2}}\right)}_{\text{6}}\right]}^{\text{2+}}$ complex is +3 and the electronic configuration of ${\text{Zn}}^{\text{2+}}$ is $\left[\text{Ar}\right]{\text{3d}}^{\text{10}}$ and it is an octahedral complex.  In an octahedral complex there are six ligands attached to the central transition metal. The d-orbital splits into two different levels.  The bottom three energy levels are ${\text{d}}_{\text{xy}}\text{,}{\text{d}}_{\text{xz}}\text{,}{\text{d}}_{\text{yz}}$ named as $\left({\text{t}}_{\text{2g}}\right)$ and the two upper levels are ${\text{d}}_{{\text{x}}^{\text{2}}{\text{-y}}^{\text{2}}}\text{\&}{\text{d}}_{{\text{z}}^{\text{2}}}$ named as ${\text{e}}_{\text{g}}$ set.

The orbital energy level diagram for ${\text{d}}^{\text{10}}$ configuration is,

Since, water acts as a strong ligand in ${\left[\text{Zn}{\left({\text{OH}}_{\text{2}}\right)}_{\text{6}}\right]}^{\text{2+}}$ complex all the d electrons are paired up in the lower energy levels and there is no unpaired electron.

(b)

Interpretation Introduction

Interpretation:

The orbital energy level diagram and the number of unpaired electrons in ${\left[\text{Co}{\left(\text{Cl}\right)}_{\text{4}}\right]}^{\text{2-}}$ complex have to be given.

Explanation of Solution

The oxidation number of cobalt in ${\left[\text{Co}{\left(\text{Cl}\right)}_{\text{4}}\right]}^{\text{2-}}$ complex is +2 and the electronic configuration of ${\text{Co}}^{\text{2+}}$ is $\left[\text{Ar}\right]{\text{3d}}^{\text{7}}$ and it is a tetrahedral complex.  In a tetrahedral complex there are four ligands attached to the central metal.  The d-orbitals split into two different energy levels.  The two three consist of ${\text{d}}_{\text{xy}}\text{,}{\text{d}}_{\text{xz}}\text{,}{\text{d}}_{\text{yz}}$ and the bottom two consist of ${\text{d}}_{{\text{x}}^{\text{2}}{\text{-y}}^{\text{2}}}\text{\&}{\text{d}}_{{\text{z}}^{\text{2}}}$ the reason for this id due to the poor orbital overlap between the metal and the ligand orbitals

The orbital energy level diagram for ${\text{d}}^7$ configuration is,

Since, chloride ion is a weak ligand the electrons are filled according to the Hund’s rule in the d-orbitals and the number of unpaired electron in cobalt complex is three.

(c)

Interpretation Introduction

Interpretation:

The orbital energy level diagram and the number of unpaired electrons in ${\left[\text{Co}{\left(\text{CN}\right)}_{\text{6}}\right]}^{\text{3-}}$ complex have to be given.

Explanation of Solution

The oxidation number of iron in ${\left[\text{Co}{\left(\text{CN}\right)}_{\text{6}}\right]}^{\text{3-}}$ complex is +3 and the electronic configuration of ${\text{Co}}^{\text{3+}}$ is $\left[\text{Ar}\right]{\text{3d}}^6$ and it is an octahedral complex.  In an octahedral complex there are six ligands attached to the central transition metal.  The d-orbital splits into two different levels.  The bottom three energy levels are ${\text{d}}_{\text{xy}}\text{,}{\text{d}}_{\text{xz}}\text{,}{\text{d}}_{\text{yz}}$ named as $\left({\text{t}}_{\text{2g}}\right)$ and the two upper levels are ${\text{d}}_{{\text{x}}^{\text{2}}{\text{-y}}^{\text{2}}}\text{\&}{\text{d}}_{{\text{z}}^{\text{2}}}$ named as ${\text{e}}_{\text{g}}$ set.

The orbital energy level diagram for ${\text{d}}^6$ configuration is,

Since, cyanide acts as a strong ligand in ${\left[\text{Co}{\left(\text{CN}\right)}_{\text{6}}\right]}^{\text{3-}}$ complex all the d electrons are paired up in the lower energy levels and there is no unpaired electron.

(d)

Interpretation Introduction

Interpretation:

The orbital energy level diagram and the number of unpaired electrons in ${\left[\text{Co}{\left(\text{F}\right)}_{\text{6}}\right]}^{\text{3-}}$ complex have to be given.

Explanation of Solution

The oxidation number of iron in ${\left[\text{Co}{\left(\text{F}\right)}_{\text{6}}\right]}^{\text{3-}}$ complex is +3 and the electronic configuration of ${\text{Co}}^{\text{3+}}$ is $\left[\text{Ar}\right]{\text{3d}}^6$ and it is an octahedral complex.  In an octahedral complex there are six ligands attached to the central transition metal.  The d-orbital splits into two different levels.  The bottom three energy levels are ${\text{d}}_{\text{xy}}\text{,}{\text{d}}_{\text{xz}}\text{,}{\text{d}}_{\text{yz}}$ named as $\left({\text{t}}_{\text{2g}}\right)$ and the two upper levels are ${\text{d}}_{{\text{x}}^{\text{2}}{\text{-y}}^{\text{2}}}\text{\&}{\text{d}}_{{\text{z}}^{\text{2}}}$ named as ${\text{e}}_{\text{g}}$ set.

The orbital energy level diagram for ${\text{d}}^6$ configuration is,

Since, fluoride ion is a weak ligand the electrons are filled according to the Hund’s rule in the d-orbitals and the number of unpaired electron in cobalt complex is four.