Question

Name the following coordination compounds. a. $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_2$ b. $\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]{\mathrm{I}}_3$ c. ${\mathrm{K}}_2\left[{\mathrm{PtC}}_4\right]$ d. ${\mathrm{K}}_4\left[\mathrm{Pt}{\mathrm{C}}_6\right]$ e. $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2$ f. $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_3{\left({\mathrm{NO}}_2\right)}_3\right]$

Short answer

a. hexaamminecobalt(III) chloride b. hexaaquacobalt(III) iodide c. potassium tetracyanidoplatinate(II) d. potassium hexacyanidoplatinate(IV) e. pentaamminechloridocobalt(III) chloride f. triamminetrinitritocobalt(III)

Step-by-step solution

1. Identify the cation and anion

The cation is the complex ion ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{2+}$, and the anion is ${\mathrm{Cl}}^{-}$.

2. Name the ligands

The ligand is NH3, which is called ammine.

3. Name the complex ion

The complex ion is named as: hexaamminecobalt(III).

4. Combine the names

The full name of the compound is: hexaamminecobalt(III) chloride. b. $\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]{\mathrm{I}}_3$

1. Identify the cation and anion

The cation is the complex ion ${\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}$, and the anion is ${\mathrm{I}}^{-}$.

2. Name the ligands

The ligand is H2O, which is called aqua.

3. Name the complex ion

The complex ion is named as: hexaaquacobalt(III).

4. Combine the names

The full name of the compound is: hexaaquacobalt(III) iodide. c. ${\mathrm{K}}_2\left[{\mathrm{PtC}}_4\right]$

1. Identify the cation and anion

The cation is ${\mathrm{K}}^{+}$, and the anion is the complex ion ${\left[{\mathrm{PtC}}_4\right]}^{2-}$.

2. Name the ligands

The ligand is cyanide (CN-), which is called cyanido.

3. Name the complex ion

The complex ion is named as: tetracyanidoplatinate(II).

4. Combine the names

The full name of the compound is: potassium tetracyanidoplatinate(II). d. ${\mathrm{K}}_4\left[\mathrm{Pt}{\mathrm{C}}_6\right]$

1. Identify the cation and anion

The cation is ${\mathrm{K}}^{+}$, and the anion is the complex ion ${\left[{\mathrm{PtC}}_6\right]}^{4-}$.

2. Name the ligands

The ligand is cyanide (CN-), which is called cyanido.

3. Name the complex ion

The complex ion is named as: hexacyanidoplatinate(IV).

4. Combine the names

The full name of the compound is: potassium hexacyanidoplatinate(IV). e. $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2$

1. Identify the cation and anion

The cation is the complex ion ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]}^{2+}$, and the anion is ${\mathrm{Cl}}^{-}$.

2. Name the ligands

The ligands are NH3, called ammine, and Cl-, called chlorido.

3. Name the complex ion

The complex ion is named as: pentaamminechloridocobalt(III).

4. Combine the names

The full name of the compound is: pentaamminechloridocobalt(III) chloride. f. $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_3{\left({\mathrm{NO}}_2\right)}_3\right]$

1. Name the ligands

The ligands are NH3, called ammine and NO2-, called nitrito.

2. Name the complex ion

The complex ion is named as: triamminetrinitritocobalt(III).

3. Combine the names

Since the compound is neutral, there is no need to include cation or anion names. The name of the compound is: triamminetrinitritocobalt(III).

Key concepts

Coordination Chemistry

Coordination chemistry is a fascinating branch of chemistry focused on the study of coordination compounds, which are molecules that consist of a central metal atom or ion bonded to surrounding molecules or ions called ligands. These compounds are significant across many industries, including medicine, catalysis, and materials science.
Coordination compounds exhibit unique properties due to the interaction of metals with ligands. These metal-ligand interactions affect the color, reactivity, and magnetic properties of the compound.
To understand coordination chemistry, it's essential to look at a few critical components:

• Central Metal Ion: At the heart of every coordination compound is a metal, typically transition metals like cobalt (Co) or platinum (Pt), which can bind to ligands through coordinate covalent bonds.
• Coordination Number: This number represents how many ligand donor atoms are attached to the central metal. For example, in a hexacoordinate compound such as $[\text{Co}({\text{NH}}_3{)}_6{]}^{2+}$, the coordination number is 6 because six ammonia molecules are bonded to cobalt.
• Geometry: Depending on its coordination number, a coordination compound can have various geometries such as octahedral, square planar, or tetrahedral. These geometrical shapes significantly impact the compound's properties.

Understanding these basic components and how they come together forms the backbone of studying and categorizing coordination compounds.

Ligand Naming

Ligand naming in coordination chemistry is crucial as it provides essential information about a coordination compound's structure. Ligands are ions or molecules capable of donating a pair of electrons to a metal ion to form a coordinate covalent bond.
There are systematic rules to naming ligands, which help in clearly identifying the composition and arrangement within a coordination compound. Here are some key aspects to remember:

• Neutral Ligands: These keep their common names, but there are exceptions. For example, water is called aqua and ammonia is called ammine when they act as ligands.
• Anionic Ligands: These ligands often have their name ending in '-ido'. For example, the cyanide ion (CN-) becomes cyanido.
• Organic Ligands: When ligands are organic, their names can become more complex, following specific rules set by IUPAC.

These naming conventions serve as a common language for chemists, ensuring that the structure and composition of coordination compounds are easily communicated among scientists globally.

Chemical Nomenclature

Chemical nomenclature is a systematic method of naming chemical compounds. It's like learning a new language, one that allows chemists to effectively share data and findings. In coordination chemistry, nomenclature is particularly important because it provides a clear method of identifying compounds with multiple components.
Naming coordination compounds involves a sequence of steps:

• Identify and name the ligands first. List them alphabetically, irrespective of their type (neutral or anionic).
• Determine the oxidation state of the central metal, which is often denoted in Roman numerals in parentheses after the metal's name.
• The name of the metal atom or ion itself follows the ligands. If the complex is an anion, the metal’s name often ends with '-ate'.

Following these rules, a compound such as $[\text{Co}({\text{NH}}_3{)}_6]{\text{Cl}}_3$ becomes hexaamminecobalt(III) chloride. These steps ensure that the naming of coordination compounds is consistent, allowing scientists to correctly interpret the chemical composition from the name alone.