Chapter 20, Problem 20.15QP

(a)

Interpretation Introduction

Interpretation: Systematic name of ${{\text{[Co(NH}}_{\text{3}}{\text{)}}_{\text{4}}{\text{Cl}}_{\text{2}}\text{]}}^{+}$ has to be determined.

Concept Introduction:

Coordination compounds: The compounds having coordination covalent bonds which form when metal ions react with polar molecules or anions.

Ligands: The ions or molecules that forms coordination covalent bond with metal ions in a coordination compound. Ligands should have minimum one lone pair of electron, where it donates two electrons to the metal. Metal atom accepts the electron pair from a ligand forming a coordination bond.

Monodentate ligand is ligands which donate only one pair of electrons to form bond with metal. It only makes one bond with metal. Polydentate ligand forms two or more coordination bond with metal ions to form a complex.

Oxidation number: The total number of electrons in an atom after losing or gaining electrons to make a bond with another atom. It indicates the charge of an ion.

The rule to name a coordination complex is,

1. 1. The cation is named before the anion.
2. 2. Within a complex ion, the Ligands are arranged in an alphabetical order followed by the metal ion name. The anionic Ligand should ends with a letter –o, the neutral Ligand are called by the molecules (some common name for some exception).
3. 3. When more Ligands are present, Greek prefixes like di, tri, tetra, penta, and hexa to specify their number.
4. 4. The oxidation number of the metal is represented in roman numerals immediately following the metal ion name.
5. 5. If the complex ion is an anion, the metal name should end with –ate.

Spectrochemical series: The list of ligands arranged in an ascending order of ligand strength.

$\begin{array}{l}\stackrel{{}^{{\text{I}}^{\text{-}}\text{<}{\text{Br}}^{\text{-}}\text{<}{\text{SCN}}^{\text{-}}\text{<}{\text{Cl}}^{\text{-}}\text{<}{\text{S}}^{\text{2-}}\text{<}{\text{F}}^{\text{-}}\text{<}{\text{OH}}^{\text{-}}\text{<}{\text{O}}^{\text{2-}}\text{<}{\text{H}}_{\text{2}}\text{O}\text{<}{\text{NCS}}^{\text{-}}\text{<}{\text{edta}}^{\text{4-}}\text{<}{\text{NH}}_{\text{3}}\text{< en}\text{<}{\text{NO}}^{\text{2-}}\text{<}{\text{CN}}^{\text{-}}\text{<}\text{CO}}}{\to }\\ {}_{{}^{{}^{\begin{array}{l}\text{weak-field}\text{increasing ligand strength}\text{strong-field}\\ \text{ligands}\text{ligands}\end{array}}}}\end{array}$

Answer to Problem 20.15QP

Systematic name of ${{\text{[Co(NH}}_{\text{3}}{\text{)}}_{\text{4}}{\text{Cl}}_{\text{2}}\text{]}}^{+}$ is tetraamminedichlorocobalt(III) ion

Explanation of Solution

Given species is ${{\text{[Co(NH}}_{\text{3}}{\text{)}}_{\text{4}}{\text{Cl}}_{\text{2}}\text{]}}^{+}$

The Ligands are arranged in an alphabetical order, followed by the metal name (cobalt). There are two $Cl$ and four $N{H}_3$ molecules.

The ligands can be written as,

$\begin{array}{l}Cl\underset{}{\to }chloro\\ {\text{NH}}_{\text{3}}\underset{}{\to }\text{ammine}\end{array}$

$\begin{array}{c}\text{Oxidation number of}{\text{NH}}_3\text{=}0\\ \text{Oxidation number of}Cl\text{=}-1\end{array}$

The charge of the complex is $1+$.

${\text{[Co(NH}}_{\text{3}}{\text{)}}_{\text{4}}{\text{Cl}}_{\text{2}}\text{]}=1+$

Therefore,

$\begin{array}{c}{\text{[Co(NH}}_{\text{3}}{\text{)}}_{\text{4}}{\text{Cl}}_{\text{2}}\text{]}=1+\\ \\ x+\left(4\times 0\right)+\left(2\times \left(-1\right)\right)=1+\\ \\ x=+3\\ \\ \text{Co}=+3\end{array}$

The oxidation state of central metal atom $Co$ is $3+$ and is represented by Roman numeral $\left(III\right)$. The overall charge of the complex is $1+$

Therefore,

The name of the ion is tetraamminedichlorocobalt(III) ion

(b)

Interpretation Introduction

Interpretation: Systematic name of ${\text{Cr(NH}}_{\text{3}}{\text{)}}_{\text{3}}{\text{Cl}}_{\text{3}}$ has to be determined.

Concept Introduction:

Coordination compounds: The compounds having coordination covalent bonds which form when metal ions react with polar molecules or anions.

Ligands: The ions or molecules that forms coordination covalent bond with metal ions in a coordination compound. Ligands should have minimum one lone pair of electron, where it donates two electrons to the metal. Metal atom accepts the electron pair from a ligand forming a coordination bond.

Monodentate ligand is ligands which donate only one pair of electrons to form bond with metal. It only makes one bond with metal. Polydentate ligand forms two or more coordination bond with metal ions to form a complex.

Oxidation number: The total number of electrons in an atom after losing or gaining electrons to make a bond with another atom. It indicates the charge of an ion.

The rule to name a coordination complex is,

1. 1. The cation is named before the anion.
2. 2. Within a complex ion, the Ligands are arranged in an alphabetical order followed by the metal ion name. The anionic Ligand should ends with a letter –o, the neutral Ligand are called by the molecules (some common name for some exception).
3. 3. When more Ligands are present, Greek prefixes like di, tri, tetra, penta, and hexa to specify their number.
4. 4. The oxidation number of the metal is represented in roman numerals immediately following the metal ion name.
5. 5. If the complex ion is an anion, the metal name should end with –ate.

Spectrochemical series: The list of ligands arranged in an ascending order of ligand strength.

$\begin{array}{l}\stackrel{{}^{{\text{I}}^{\text{-}}\text{<}{\text{Br}}^{\text{-}}\text{<}{\text{SCN}}^{\text{-}}\text{<}{\text{Cl}}^{\text{-}}\text{<}{\text{S}}^{\text{2-}}\text{<}{\text{F}}^{\text{-}}\text{<}{\text{OH}}^{\text{-}}\text{<}{\text{O}}^{\text{2-}}\text{<}{\text{H}}_{\text{2}}\text{O}\text{<}{\text{NCS}}^{\text{-}}\text{<}{\text{edta}}^{\text{4-}}\text{<}{\text{NH}}_{\text{3}}\text{< en}\text{<}{\text{NO}}^{\text{2-}}\text{<}{\text{CN}}^{\text{-}}\text{<}\text{CO}}}{\to }\\ {}_{{}^{{}^{\begin{array}{l}\text{weak-field}\text{increasing ligand strength}\text{strong-field}\\ \text{ligands}\text{ligands}\end{array}}}}\end{array}$

Answer to Problem 20.15QP

Systematic name of ${\text{Cr(NH}}_{\text{3}}{\text{)}}_{\text{3}}{\text{Cl}}_{\text{3}}$ is triamminetrichlorochromium(III).

Explanation of Solution

Given species is ${\text{Cr(NH}}_{\text{3}}{\text{)}}_{\text{3}}{\text{Cl}}_{\text{3}}$

The Ligands are arranged in an alphabetical order, followed by the metal name (chromium). There are three $N{H}_3$ and $Cl$ molecule.

The ligands can be written as,

$\begin{array}{l}Cl\underset{}{\to }chloro\\ {\text{NH}}_{\text{3}}\underset{}{\to }\text{ammine}\end{array}$

$\begin{array}{c}\text{Oxidation number of}{\text{NH}}_3\text{=}0\\ \text{Oxidation number of}Cl\text{=}-1\end{array}$

The charge of the complex is zero.

${\text{Cr(NH}}_{\text{3}}{\text{)}}_{\text{3}}{\text{Cl}}_{\text{3}}=0$

Therefore,

$\begin{array}{c}{\text{Cr(NH}}_{\text{3}}{\text{)}}_{\text{3}}{\text{Cl}}_{\text{3}}=0\\ \\ x+\left(3\times 0\right)+\left(3\times \left(-1\right)\right)=0\\ \\ x=+3\\ \\ \text{Cr}=+3\end{array}$

The oxidation state of central metal atom $Cr$ is $3+$ and is represented by Roman numeral $\left(III\right)$. The overall charge of the complex is zero

Therefore,

The name of the ion is triamminetrichlorochromium(III)

(c)

Interpretation Introduction

Interpretation: Systematic name of ${{\text{[Co(en)}}_{\text{2}}{\text{Br}}_{\text{2}}\text{]}}^{+}$ has to be determined.

Concept Introduction:

Coordination compounds: The compounds having coordination covalent bonds which form when metal ions react with polar molecules or anions.

Ligands: The ions or molecules that forms coordination covalent bond with metal ions in a coordination compound. Ligands should have minimum one lone pair of electron, where it donates two electrons to the metal. Metal atom accepts the electron pair from a ligand forming a coordination bond.

Monodentate ligand is ligands which donate only one pair of electrons to form bond with metal. It only makes one bond with metal. Polydentate ligand forms two or more coordination bond with metal ions to form a complex.

Oxidation number: The total number of electrons in an atom after losing or gaining electrons to make a bond with another atom. It indicates the charge of an ion.

The rule to name a coordination complex is,

1. 1. The cation is named before the anion.
2. 2. Within a complex ion, the Ligands are arranged in an alphabetical order followed by the metal ion name. The anionic Ligand should ends with a letter –o, the neutral Ligand are called by the molecules (some common name for some exception).
3. 3. When more Ligands are present, Greek prefixes like di, tri, tetra, penta, and hexa to specify their number.
4. 4. The oxidation number of the metal is represented in roman numerals immediately following the metal ion name.
5. 5. If the complex ion is an anion, the metal name should end with –ate.

Spectrochemical series: The list of ligands arranged in an ascending order of ligand strength.

$\begin{array}{l}\stackrel{{}^{{\text{I}}^{\text{-}}\text{<}{\text{Br}}^{\text{-}}\text{<}{\text{SCN}}^{\text{-}}\text{<}{\text{Cl}}^{\text{-}}\text{<}{\text{S}}^{\text{2-}}\text{<}{\text{F}}^{\text{-}}\text{<}{\text{OH}}^{\text{-}}\text{<}{\text{O}}^{\text{2-}}\text{<}{\text{H}}_{\text{2}}\text{O}\text{<}{\text{NCS}}^{\text{-}}\text{<}{\text{edta}}^{\text{4-}}\text{<}{\text{NH}}_{\text{3}}\text{< en}\text{<}{\text{NO}}^{\text{2-}}\text{<}{\text{CN}}^{\text{-}}\text{<}\text{CO}}}{\to }\\ {}_{{}^{{}^{\begin{array}{l}\text{weak-field}\text{increasing ligand strength}\text{strong-field}\\ \text{ligands}\text{ligands}\end{array}}}}\end{array}$

Answer to Problem 20.15QP

The name of the ion is dibromobis(ethylenediamine)cobalt(III)ion

Explanation of Solution

Given species is ${{\text{[Co(en)}}_{\text{2}}{\text{Br}}_{\text{2}}\text{]}}^{+}$

The Ligands are arranged in an alphabetical order, followed by the metal name (cobalt). There are two en and $Br$ molecules.

The ligands can be written as,

$\begin{array}{l}\text{en}\underset{}{\to }\text{ethylenediamine}\\ \text{Br}\underset{}{\to }\text{bromo}\end{array}$

$\begin{array}{c}\text{Oxidation number of}en\text{=}0\\ \text{Oxidation number of}Br\text{=}-1\end{array}$

The charge of the complex is $1+$.

${\text{[Co(en)}}_{\text{2}}{\text{Br}}_{\text{2}}\text{]}=1+$

Therefore,

$\begin{array}{c}{\text{[Co(en)}}_{\text{2}}{\text{Br}}_{\text{2}}\text{]}=1+\\ \\ x+\left(2\times 0\right)+\left(2\times \left(-1\right)\right)=1+\\ \\ x=+3\\ \\ \text{Co}=+3\end{array}$

The oxidation state of central metal atom $Co$ is $3+$ and is represented by Roman numeral $\left(III\right)$. The overall charge of the complex is $1+$

Therefore,

The name of the ion is dibromobis(ethylenediamine)cobalt(III)ion

(d)

Interpretation Introduction

Interpretation: Systematic name of ${\text{Fe(CO)}}_{\text{5}}$ has to be determined.

Concept Introduction:

Coordination compounds: The compounds having coordination covalent bonds which form when metal ions react with polar molecules or anions.

Ligands: The ions or molecules that forms coordination covalent bond with metal ions in a coordination compound. Ligands should have minimum one lone pair of electron, where it donates two electrons to the metal. Metal atom accepts the electron pair from a ligand forming a coordination bond.

Monodentate ligand is ligands which donate only one pair of electrons to form bond with metal. It only makes one bond with metal. Polydentate ligand forms two or more coordination bond with metal ions to form a complex.

Oxidation number: The total number of electrons in an atom after losing or gaining electrons to make a bond with another atom. It indicates the charge of an ion.

The rule to name a coordination complex is,

1. 1. The cation is named before the anion.
2. 2. Within a complex ion, the Ligands are arranged in an alphabetical order followed by the metal ion name. The anionic Ligand should ends with a letter –o, the neutral Ligand are called by the molecules (some common name for some exception).
3. 3. When more Ligands are present, Greek prefixes like di, tri, tetra, penta, and hexa to specify their number.
4. 4. The oxidation number of the metal is represented in roman numerals immediately following the metal ion name.
5. 5. If the complex ion is an anion, the metal name should end with –ate.

Spectrochemical series: The list of ligands arranged in an ascending order of ligand strength.

$\begin{array}{l}\stackrel{{}^{{\text{I}}^{\text{-}}\text{<}{\text{Br}}^{\text{-}}\text{<}{\text{SCN}}^{\text{-}}\text{<}{\text{Cl}}^{\text{-}}\text{<}{\text{S}}^{\text{2-}}\text{<}{\text{F}}^{\text{-}}\text{<}{\text{OH}}^{\text{-}}\text{<}{\text{O}}^{\text{2-}}\text{<}{\text{H}}_{\text{2}}\text{O}\text{<}{\text{NCS}}^{\text{-}}\text{<}{\text{edta}}^{\text{4-}}\text{<}{\text{NH}}_{\text{3}}\text{< en}\text{<}{\text{NO}}^{\text{2-}}\text{<}{\text{CN}}^{\text{-}}\text{<}\text{CO}}}{\to }\\ {}_{{}^{{}^{\begin{array}{l}\text{weak-field}\text{increasing ligand strength}\text{strong-field}\\ \text{ligands}\text{ligands}\end{array}}}}\end{array}$

Answer to Problem 20.15QP

Systematic name of ${\text{Fe(CO)}}_{\text{5}}$ is pentacarbonyliron(0)

Explanation of Solution

Given species is ${\text{Fe(CO)}}_{\text{5}}$

The Ligands are arranged in an alphabetical order, followed by the metal name (iron). There are two $CO$ molecules.

The ligands can be written as,

$\text{CO}\underset{}{\to }\text{carbonyl}$

$\text{Oxidation number of}CO\text{=}0$

The charge of the complex is zero.

${\text{Fe(CO)}}_{\text{5}}=0$

Therefore,

$\begin{array}{c}{\text{Fe(CO)}}_{\text{5}}=0\\ \\ x+\left(5\times 0\right)=0\\ \\ x=0\\ \\ \text{Fe}=0\end{array}$

The oxidation state of central metal atom $Fe$ is zero. The overall charge of the complex is zero

Therefore,

The name of the complex is pentacarbonyliron(0)