Problem 83 - General Chemistry

Question

What is the name of \(\mathrm{K}_{2}[\mathrm{MoOCl}]_{4}\) ?

Step-by-Step Solution

Answer

The compound is called dipotassium tetrachlorodioxomolybdenum(IV).

Step 1: Understand the Coordination Compound

The given compound is \(\mathrm{K}_{2}[\mathrm{MoOCl}]_{4}\). This is a coordination compound where \(\mathrm{K}_{2}\) represents the cations and \([\mathrm{MoOCl}]_{4}\) is the coordination complex. We need to name the complex inside the brackets first.

Step 2: Determine the Central Metal

The central metal atom in the coordination complex is Molybdenum (Mo). In coordination chemistry, the oxidation state of the central metal is often indicated in Roman numerals. We need to determine the oxidation state of Mo in this complex.

Step 3: Calculate the Oxidation State of Mo

Consider the oxidation state of each component within the complex. Oxygen typically has an oxidation state of -2, and chloride (Cl) has an oxidation state of -1. Potassium (K), being a typical alkali metal, has an oxidation state of +1. Let the oxidation state of Mo be \(x\). The complex \([\mathrm{MoOCl}]_{4}\) is assumed to be neutral, so we write the equation for a single complex unit:\[ x + (-2) + 4(-1) = -2 \]Given two positive charges from potassium ions (2 x +1 = +2), the total charge balance of the complex becomes -2 for one \([\mathrm{MoOCl}]_{4}\) unit: \[ x - 2 - 4 = -2 \]\[ x = +4 \]Therefore, the oxidation number of Mo is +4.

Step 4: Name the Complex Ligand

The ligand in the complex is an oxo (O) and chloro (Cl) combination, which are simple ligands. We list the ligands alphabetically when naming: 'chloro' comes before 'oxo'.

Step 5: Assemble the Name of the Coordination Compound

We combine the information with the central metal. The complex \([\mathrm{MoOCl}]_{4}\) is thus named 'tetrachlorodioxomolybdenum(IV)', considering it has four chloride ions and one oxo ligand. Potassium is added as the cation prefix, resulting in the complete name: 'dipotassium tetrachlorodioxomolybdenum(IV)'.

Key Concepts

Molybdenum Oxidation State

In coordination compounds, understanding the oxidation state of the central metal is crucial for their naming and understanding their properties. The oxidation state reflects the number of electrons the metal can exchange with its ligands. For the compound \([\mathrm{MoOCl}]_4\), molybdenum (Mo) is our central metal.

To find its oxidation state, consider the other species in the compound. Oxygen typically has an oxidation state of \(-2\), while chloride (\(\text{Cl}\)) is typically \(-1\). Because the complex is surrounded by two \(\text{K}^+\) ions, which balance the charge, the coordination sphere should have a charge of \(-2\).

The equation for determining the oxidation state of Mo becomes:

• Mo: \(x\)
• O: \(-2\)
• 4 Cl: \(4\times(-1) = -4\)

Thus: \[ x + (-2) - 4 = -2 \]Simplifying, we find \(x = +4\). Therefore, the oxidation state of molybdenum in this compound is \(+4\). Understanding this helps us name the compound correctly and predict possible chemical behaviors.

Ligand Naming

Ligands are the ions or molecules attached to the central metal in a coordination compound. They play a significant role in compound naming and in determining the chemical behavior of the compound.

In the compound \([\mathrm{MoOCl}]_4\), molybdenum is bound to an "oxo" (O) ligand and a number of "chloro" (Cl) ligands. When naming these ligands:

• Oxide ligands are referred to as "oxo".
• Chloride ligands are called "chloro".

When writing the name of the complex, it is important to list ligands in alphabetical order. This ensures consistency in chemical nomenclature.

• "Chloro" comes before "oxo", alphabetically.

Therefore, when naming \([\mathrm{MoOCl}]_4\), and taking into account the ligands, it becomes "tetrachlorodioxomolybdenum".
Understanding the naming of ligands is essential as it helps in predicting the number of each ligand and their overall impact on the chemistry of the compound.

Coordination Chemistry Fundamentals

Coordination chemistry revolves around the formation of coordination compounds, which typically consist of a central metal and surrounding ligands.

These structures are important for understanding various chemical reactions and are foundational in inorganic chemistry studies. In a coordination complex:

• The central metal, often a transition metal like molybdenum (Mo) in our example, is key.
• Ligands can be ions or neutral molecules that donate pairs of electrons to the metal.
• Coordination number, which is the count of ligand atoms bound to the central metal, is vital.

For \([\mathrm{MoOCl}]_4\), a common interaction between the metal and ligands involves electron donation, creating a stable entity.
Moreover, coordination compounds can have wide applications, from catalysis to medical treatments, as they can substantially alter the properties of a compound. By learning the fundamentals, one can predict interactions and properties of numerous coordination complexes encountered in chemistry.