Question

Write the names of the following compounds, using the standard nomenclature rules for coordination complexes: (a) \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{NO}_{3}\) (b) \(\mathrm{Hg}\left[\mathrm{Co}(\mathrm{SCN})_{4}\right]\) (c) \(\left[\mathrm{Ru}\left(\mathrm{PPh}_{3}\right)_{3} \mathrm{Cl}_{3}\right]\) (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{CO}_{3}\right]_{2} \mathrm{SO}_{4}\)

Short answer

The names of the coordination complexes are: (a) di_ammine_silver(I) nitrate (b) mercury(II) tetra_thiocyanatocobalt(III) (c) tri_phosphinetriphenyl_tri_chlororuthenium (d) penta_amminecarbonatocobalt(II) sulfate

Step-by-step solution

Naming Complex (a)

The given complex is \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{NO}_{3}\), where 'Ag' is the metal, 'NH3' is the ligand, and 'NO3' is the counter-ion. Naming the complex: 1. Metal name: Silver (for Ag) 2. Ligand name: di_ammine (for two NH3 ligands) 3. Charge: Since Ag has a +1 charge, the entire complex ion has a +1 charge as well. Therefore, we use (I) for the overall charge. 4. Counter-ion name: Nitrate (for NO3) Hence, the name of the compound is: di_ammine_silver(I) nitrate.

Naming Complex (b)

The given complex is \(\mathrm{Hg}\left[\mathrm{Co}(\mathrm{SCN})_{4}\right]\), where 'Hg' is the counter-ion and '[Co(SCN)4]' is the coordination complex with 'Co' as the metal and 4 'SCN' ligands. Naming the complex: 1. Metal name: Cobalt (for Co) 2. Ligand name: tetra_thiocyanato (for four SCN ligands) 3. Charge: Cobalt generally has +2 and +3 oxidation states. Since there are 4 negatively charged SCN ligands, the charge on Co in this complex is +3. Therefore, we use (III) for the overall charge. 4. Counter-ion name: Mercury(II) (for Hg with a +2 charge) The name of the compound is: mercury(II) tetra_thiocyanatocobalt(III).

Naming Complex (c)

The given complex is \(\left[\mathrm{Ru}\left(\mathrm{PPh}_{3}\right)_{3}\mathrm{Cl}_{3}\right]\), with 'Ru' as the metal, 3 'PPh3' and 3 'Cl' as ligands. Naming the complex: 1. Metal name: Ruthenium (for Ru) 2. Ligand names: tri_phosphinetriphenyl(triPPh3 ligands), tri_chloro (three Cl ligands) 3. Charge: There's no overall charge on the complex. Hence, the name of the compound is: tri_phosphinetriphenyl_tri_chlororuthenium.

Naming Complex (d)

The given complex is \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\mathrm{CO}_{3}\right]_{2} \mathrm{SO}_{4}\), where 'Co' is the metal, 5 'NH3' and 1 'CO3' are the ligands, and 'SO4' is the counter-ion. Naming the complex: 1. Metal name: Cobalt (for Co) 2. Ligand names: penta_ammine (five NH3 ligands), carbonato (one CO3 ligand) 3. Charge: The sulfate ion has a -2 charge, which means the complex ion has a +2 charge. Thus, we use (II) for the overall charge. 4. Counter-ion name: Sulfate (for SO4) The name of the compound is: penta_amminecarbonatocobalt(II) sulfate.

Key concepts

Ligands

In coordination chemistry, ligands are molecules or ions that bind to a central metal atom to form a coordination complex. They can be thought of as the "hands" that hold onto the metal, forming a stable structure. Ligands typically have at least one pair of electrons available to be shared with the metal ion.

The type and number of ligands in a complex can significantly influence the properties and the nomenclature of the coordination compound. For example, in \([\text{Ag}\text{(NH}_3\text{)}_{2}] \text{NO}_3\) from the original exercise, "NH₃" is the ligand. Because there are two ammonia (NH₃) molecules attached to the silver, we use the term "diammine" to describe these two ligands in the name of the compound.

Ligands can vary in their electron donation ability, forming either weaker or stronger bonds with the metal center. The nature of these bonds and the arrangement around the metal atom help determine the stability and reactivity of the complex.

Transition Metals

Transition metals hold a central place in coordination complexes due to their ability to form various oxidation states and coordinate with multiple ligands. These metals, often found in the central portion of the periodic table, include elements like silver (Ag), cobalt (Co), and ruthenium (Ru), all of which appear in the exercise examples.

Transition metals are characterized by their partially filled d-orbitals, which allow them to form complex ions with various geometric structures. For instance, in \([\mathrm{Co}(\mathrm{NH}_{3})_{5}\mathrm{CO}_{3}]_{2} \mathrm{SO}_{4}\), cobalt acts as the central metal atom bonding with five ammonia and one carbonate ligand, forming a complex ion.

Understanding the role of transition metals is crucial when determining the name and architecture of coordination compounds. They provide the framework around which ligands can organize and form the overall chemical structure.

Oxidation States

Oxidation states indicate the degree of oxidation of an atom in a chemical compound. In coordination chemistry, knowing the oxidation state of the central metal atom is essential. It determines how many electrons the metal is sharing with its ligands and influences the naming of the compound.

For example, in the complex \([\mathrm{Co}(\mathrm{SCN})_4]\), the four SCN ligands each carry a -1 charge. Given cobalt's potential oxidation states of +2 and +3, the sum of the charges can help us ascertain the metal’s oxidation state. With four SCN ions, the oxidation state of cobalt in this particular complex is +3.

Understanding and identifying oxidation states are not only fundamental for proper nomenclature but also for predicting the compound's reactivity and physical properties.

Complex Ions

Complex ions are charged species consisting of a central metal atom bonded to one or more ligands. These complexes can carry either a positive or a negative charge depending on the sum of the charges from their central metal and associated ligands.

A clear example from the exercise is the complex \([\mathrm{Ru}\text{(PPh}_3\text{)}_{3}\mathrm{Cl}_3]\), where the ruthenium central atom is bonded to three phosphines and three chloride ions, forming a neutral complex because the positive charge from Ru and negative charges from Cl cancel out.

Complex ions are important in coordination chemistry, not only for their remarkable structures and stability but also because they help determine the physical and chemical characteristics of a coordination compound. Naming complexes accurately reflects their composition, like calling a compound with four thiocyanate ligands a "tetra_thiocyanato" derivative, aiding in consistent scientific communication.