Chapter 21, Problem 3RQ

Interpretation Introduction

Interpretation: The geometries and bond angle for the metal ion having coordination number $2$, $4$ or $6$; the correct formulas for given complex ions and their electronic configuration are to be stated.

Concept introduction: Coordination number is the number of nearest neighbors of the given metal ion. The geometry of a coordination complex depends on the number of ligands that are surrounding a metal ion.

Answer to Problem 3RQ

Answer

When a metal ion has a coordination number of $2$, $4$ or $6$, it has geometry as linear with a bond angle of $180°$, tetrahedral with a bond angle of $109.5°$ or square planar with a bond angle of $90°$ and octahedral with a bond angle as $90°$ respectively.

1. I. The formulas for the given complex ions are,

   a. The formula of the complex is ${\left[\text{Ag}{\left(\text{CN}\right)}_2\right]}^{-}$ and bond angle is $180°$.

b. The formula of the complex is ${\left[\text{Cu}{\left({\text{H}}_2\text{O}\right)}_4\right]}^{+}$ and bond angle is $109.5°$.

c. The formula of the complex is ${\left[\text{Mn}{\left({\text{C}}_2{\text{O}}_4\right)}_2\right]}^{2-}$ and bond angle is $90°$.

d. The formula of the complex is ${\left[\text{Pt}{\left({\text{NH}}_3\right)}_4\right]}^{2+}$ and bond angle is $90°$.

e. The formula of the complex is ${\left[\text{Fe}\left(\text{EDTA}\right)\right]}^{-}$ and bond angle is $90°$.

d. The formula of the complex is ${\left[{\text{CoCl}}_6\right]}^{2+}$ and bond angle is $90°$.

f. The formula of the complex is ${\left[\text{Cr}{\left(\text{en}\right)}_3\right]}^{3+}$ and bond angle is $90°$.

1. II. The electronic configuration of metal ion in each of the complex ion is,
2. a. The electronic configuration of ${\text{Ag}}^{+}$ is $\left[\text{Kr}\right]4{\text{d}}^{10}$.
3. b. The electronic configuration of ${\text{Cu}}^{+}$ is $\left[\text{Ar}\right]3{\text{d}}^{10}$.
4. c. The electronic configuration of ${\text{Mn}}^{2+}$ is $\left[\text{Ar}\right]3{\text{d}}^{5}4{\text{s}}^1$.
5. d. The electronic configuration of ${\text{Pt}}^{2+}$ is $\left[\text{Xe}\right]4{\text{f}}^{14}5{\text{d}}^{\text{8}}$.
6. e. The electronic configuration of ${\text{Fe}}^{3+}$ is $\left[\text{Ar}\right]3{\text{d}}^5$.
7. f. The electronic configuration of ${\text{Co}}^{2+}$ is $\left[\text{Ar}\right]3{\text{d}}^7$.

Explanation of Solution

(I)

To determine: The geometry and associated bond angles when a metal ion has a coordination number of $2$, $4$ or $6$.

When a metal ion has a coordination number of $2$, it means it is linear in geometry and has a bond angle of $180°$. But, when the metal ion has coordination number of $4$ it means it is surrounded by four neighbors and therefore the geometry is tetrahedral and the angle is $109.5°$ or it can be square planar where the bond angle is $90°$. When a metal ion has a coordination number of $6$, it means it is surrounded by six neighbours and has geometry as octahedral and bond angle equal to $90°$.

(II)

(a)

To determine: The correct formula for the linear ${\text{Ag}}^{+}$ complex having ${\text{CN}}^{-}$ ligands.

Linear geometry shows that ${\text{Ag}}^{+}$ is surrounded by two ligands and therefore it has a coordination number of $2$. The formula of the complex is ${\left[\text{Ag}{\left(\text{CN}\right)}_2\right]}^{-}$ and bond angle is $180°$.

(b)

To determine: The correct formula for tetrahedral ${\text{Cu}}^{+}$ complex having ${\text{H}}_2\text{O}$ ligands.

Tetrahedral geometry shows that ${\text{Cu}}^{+}$ is surrounded by four ligands and therefore it has a coordination number of 4. The formula of the complex is ${\left[\text{Cu}{\left({\text{H}}_2\text{O}\right)}_4\right]}^{+}$ and bond angle is $109.5°$.

(c)

To determine: The correct formula for tetrahedral ${\text{Mn}}^{2+}$ complex having Oxalate ligands.

Tetrahedral geometry shows that ${\text{Mn}}^{2+}$ is surrounded by four ligands and therefore it has a coordination number of 4. The formula of the complex is ${\left[\text{Mn}{\left({\text{C}}_2{\text{O}}_4\right)}_2\right]}^{2-}$ and bond angle is $90°$.

(d)

To determine: The correct formula for square planar ${\text{Pt}}^{2+}$ complex having ${\text{NH}}_3$ ligands.

Square planar geometry shows that ${\text{Pt}}^{2+}$ is surrounded by four ligands and therefore it has a coordination number of 4. The formula of the complex is ${\left[\text{Pt}{\left({\text{NH}}_3\right)}_4\right]}^{2+}$ and bond angle is $90°$.

(e)

To determine: The correct formula for octahedral ${\text{Fe}}^{3+}$ complex ions having EDTA ligands.

An octahedral geometry shows that ${\text{Fe}}^{3+}$ is surrounded by six ligands and therefore it has a coordination number of $6$. The formula of the complex is ${\left[\text{Fe}\left(\text{EDTA}\right)\right]}^{-}$ and bond angle is $90°$.

(f)

To determine: The correct formula for octahedral ${\text{Co}}^{2+}$ complex ions having ${\text{Cl}}^{-}$ ligands.

An octahedral geometry shows that ${\text{Co}}^{2+}$ is surrounded by six ligands and therefore it has a coordination number of $6$. The formula of the complex is ${\left[{\text{CoCl}}_6\right]}^{2+}$ and bond angle is $90°$.

(g)

To determine: The correct formula for octahedral ${\text{Cr}}^{3+}$ complex ions having ethylene-diamine ligands.

Step: 7

An octahedral geometry shows that ${\text{Cr}}^{3+}$ is surrounded by six ligands and therefore it has a coordination number of $6$. The formula of the complex is ${\left[\text{Cr}{\left(\text{en}\right)}_3\right]}^{3+}$ and bond angle is $90°$.

(III)

(a)

To determine: The electronic configuration for the linear ${\text{Ag}}^{+}$ complex having ${\text{CN}}^{-}$ ligands.

The electronic configuration of $\text{Ag}$ is $\left[\text{Kr}\right]4{\text{d}}^{10}5{\text{s}}^1$. After removal of one electron it gets converted to ${\text{Ag}}^{+}$ and electronic configuration therefore changes to $\left[\text{Kr}\right]4{\text{d}}^{10}$.

(b)

To determine: The electronic configuration for tetrahedral ${\text{Cu}}^{+}$ complex having ${\text{H}}_2\text{O}$ ligands.

The electronic configuration of $\text{Cu}$ is $\left[\text{Ar}\right]3{\text{d}}^{10}4{\text{s}}^1$. After removal of one electron it gets converted to ${\text{Cu}}^{+}$ and electronic configuration therefore changes to $\left[\text{Ar}\right]3{\text{d}}^{10}$.

(c)

To determine: The electronic configuration for tetrahedral ${\text{Mn}}^{2+}$ complex having Oxalate ligands.

The electronic configuration of $\text{Mn}$ is $\left[\text{Ar}\right]3{\text{d}}^{5}4{\text{s}}^2$. After removal of two electrons, it gets converted to ${\text{Mn}}^{2+}$ and electronic configuration therefore changes to $\left[\text{Ar}\right]3{\text{d}}^5$.

(d)

To determine: The electronic configuration for square planar ${\text{Pt}}^{2+}$ complex having ${\text{NH}}_3$ ligands.

The electronic configuration of $\text{Pt}$ is $\left[\text{Xe}\right]4{\text{f}}^{14}5{\text{d}}^{9}6{\text{s}}^1$. After removal of two electrons, it gets converted to ${\text{Pt}}^{2+}$ and electronic configuration therefore changes to $\left[\text{Xe}\right]4{\text{f}}^{14}5{\text{d}}^{\text{8}}$.

(e)

To determine: The electronic configuration for octahedral ${\text{Fe}}^{3+}$ complex ions having EDTA ligands.

The electronic configuration of $\text{Fe}$ is $\left[\text{Ar}\right]{\text{3d}}^6{\text{4s}}^{\text{2}}$. After removal of three electrons it gets converted to ${\text{Fe}}^{3+}$ and electronic configuration therefore changes to $\left[\text{Ar}\right]3{\text{d}}^5$.

(f)

To determine: The electronic configuration for octahedral ${\text{Co}}^{2+}$ complex ions having ${\text{Cl}}^{-}$ ligands.

The electronic configuration of $\text{Co}$ is $\left[\text{Ar}\right]{\text{3d}}^7{\text{4s}}^{\text{2}}$. After removal of two electrons it gets converted to ${\text{Co}}^{2+}$ and electronic configuration therefore changes to $\left[\text{Ar}\right]3{\text{d}}^7$.

(g)

To determine: The correct electronic configuration for octahedral ${\text{Cr}}^{3+}$ complex ions having ethylene-diamine ligands.

The electronic configuration of $\text{Cr}$ is $\left[\text{Ar}\right]{\text{3d}}^5{\text{4s}}^1$. After removal of three electrons, it gets converted to ${\text{Cr}}^{3+}$ and electronic configuration therefore changes to $\left[\text{Ar}\right]3{\text{d}}^{\text{3}}$.

Conclusion

Conclusion

The coordination number and the availability of orbitals decide the geometry of the coordination compound and the removal of electron from a metal occurs from the shell that is far from the influence of nucleus that is the outermost shell.