Chapter 22, Problem 27PS

a.

Interpretation Introduction

Interpretation: The formula of the following ions or compounds is 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 $\text{(Δ)}$(the splitting of d-orbitals in presence of various ligands).

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

Answer to Problem 27PS

1. a) $\left[Ni{\left(en\right)}_2{\left(Cl\right)}_2\right]$

Explanation of Solution

The oxidation state of central metal atom $Ni$ is $2+$. Dichloro means there are two $Cl$ ions whereas $\text{bis}\left(\text{ethylenediamine}\right)$ means two diethylenediamine molecules are coordinated to the central atom. Each diethylenediamine forms two coordination bonds with metal ions to form a complex

The ligands can be written as,

  $\begin{array}{l}chloro\underset{}{\to }Cl\\ \text{ethylenediamine}\underset{}{\to }en\end{array}$

The oxidation state is,

  $\begin{array}{c}\text{Oxidation number of}\text{Cl}\text{=1}-\\ \text{Oxidation number of}en\text{=}0\\ \text{Oxidation number of}Ni\text{=}2+\end{array}$

The charge of the complex is,

  $\begin{array}{c}\left[Ni{\left(en\right)}_2{\left(Cl\right)}_2\right]=\left(2+\right)+\left(2\times 0\right)+\left(2\times \left(1-\right)\right)\\ =0\end{array}$

The complex is neutral

Therefore,

The formula of the complex is,

  $\left[Ni{\left(en\right)}_2{\left(Cl\right)}_2\right]$

(b)

Interpretation Introduction

Interpretation: The formula of the following ions or compounds is 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 $\text{(Δ)}$(the splitting of d-orbitals in presence of various ligands).

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

Answer to Problem 27PS

$K_2\left[PtC{l}_4\right]$

Explanation of Solution

The oxidation state of central metal atom $Pt$ is $2+$. Tetrachloro means there are four $Cl$ ions. The metal name is ended with –ate so the complex ion is an anion

The ligands can be written as,

  $chloro\underset{}{\to }Cl$

The oxidation state is,

  $\begin{array}{c}\text{Oxidation number of}\text{Cl}\text{=1}-\\ \text{Oxidation number of}K\text{=}1+\\ \text{Oxidation number of}Pt\text{=}2+\end{array}$

The charge of the complex is,

  $\begin{array}{c}{K}_2\left[PtC{l}_4\right]=\left(1\times 2\right)+\left(2\times 1\right)+\left(4\times \left(1-\right)\right)\\ =0\end{array}$

The complex is neutral

Therefore,

The formula of the complex is,

  $K_2\left[PtC{l}_4\right]$

(c)

Interpretation Introduction

Interpretation: The formula of the following ions or compounds is 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 $\text{(Δ)}$(the splitting of d-orbitals in presence of various ligands).

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

Answer to Problem 27PS

$K\left[Cu{\left(CN\right)}_2\right]$

Explanation of Solution

The oxidation state of central metal atom $Cu$ is $1+$. Dicyano means there are two $CN$ ions. The metal name is ended with –ate so the complex ion is an anion

The ligands can be written as,

  $\begin{array}{l}cyano\underset{}{\to }CN\\ cuprate\underset{}{\to }Cu\end{array}$

The oxidation state is,

  $\begin{array}{c}\text{Oxidation number of}CN\text{=1}-\\ \text{Oxidation number of}K\text{=}1+\\ \text{Oxidation number of}Cu\text{=}2+\end{array}$

The charge of the complex is,

  $\begin{array}{c}K\left[Cu{\left(CN\right)}_2\right]=\left(1\times 1\right)+\left(1\times 1\right)+\left(2\times \left(1-\right)\right)\\ =0\end{array}$

The complex is neutral

Therefore,

The formula of the complex is,

  $K\left[Cu{\left(CN\right)}_2\right]$

(d)

Interpretation Introduction

Interpretation: The formula of the following ions or compounds is 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 $\text{(Δ)}$(the splitting of d-orbitals in presence of various ligands).

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

Answer to Problem 27PS

${\left[Fe{\left(N{H}_3\right)}_4{\left(H_{2}O\right)}_2\right]}^{2+}$

Explanation of Solution

The oxidation state of central metal atom $Fe$ is $2+$. Tetraamine means there are four $N{H}_3$ ions whereas diaqua means two water molecules.

The ligands can be written as,

  $\begin{array}{l}\text{ammine}\underset{}{\to }{\text{NH}}_{\text{3}}\\ \text{aqua}\underset{}{\to }{\text{H}}_{\text{2}}\text{o}\end{array}$

The oxidation state is,

  $\begin{array}{c}\text{Oxidation number of}N{H}_3\text{=0}\\ \text{Oxidation number of}{H}_2\text{O}\text{=}0\\ \text{Oxidation number of}Fe\text{=}2+\end{array}$

The charge of the complex is,

  $\begin{array}{c}\left[Fe{\left(N{H}_3\right)}_4{\left(H_{2}O\right)}_2\right]=\left(1\times 1\right)+\left(4\times 0\right)+\left(2\times 0\right)\\ =2+\end{array}$

The charge of the complex is $2+$

Therefore,

The formula of the complex is,

  ${\left[Fe{\left(N{H}_3\right)}_4{\left(H_{2}O\right)}_2\right]}^{2+}$

Conclusion

The formula of the complex was determined,

1. a) $\left[Ni{\left(en\right)}_2{\left(Cl\right)}_2\right]$
2. b) $K_2\left[PtC{l}_4\right]$
3. c) $K\left[Cu{\left(CN\right)}_2\right]$
4. d) ${\left[Fe{\left(N{H}_3\right)}_4{\left(H_{2}O\right)}_2\right]}^{2+}$