Problem 37 - A Complete Resource Book in Chemistry for JEE Main

Question

The correct IUPAC name of \(\mathrm{Mn}_{3}(\mathrm{CO})_{12}\) is (a) manganic dodecacarbonyl (0) (b) dodecacarbonyl trimanganese (0) (c) dodecacarbonyl manganic (II) (d) dodecacarbonyl manganate (0)

Step-by-Step Solution

Answer

The correct IUPAC name is dodecacarbonyl trimanganese (0).

Step 1: Identify the ligand

The compound contains CO as a ligand, which is referred to as carbon monoxide when naming complexes. A single CO ligand is named as 'carbonyl'. Since there are twelve such carbonyl ligands, the prefix 'dodeca' is used, forming 'dodecacarbonyl'.

Step 2: Determine the number of metal atoms

The chemical formula indicates that there are three manganese (Mn) atoms. When naming a complex for multiple atoms of the same metal, the prefix specific to the count is added. Here, 'tri' is used, resulting in 'trimanganese'.

Step 3: Identify the oxidation state

In this compound, the oxidation state of manganese is zero. Since no charge or counterions are present, it is explicitly mentioned as '0' following the metal's name in parentheses.

Step 4: Combine elements for the IUPAC name

Combine the parts from the previous steps to write the full name. The format is: number of ligands + ligand name + number of metal atoms + metal name (oxidation state). Thus, the IUPAC name is 'dodecacarbonyl trimanganese (0)'.

Key Concepts

Coordination Chemistry

Coordination chemistry is a fascinating branch of chemistry that involves the study of complex compounds known as coordination complexes. These complexes consist of a central metal atom or ion surrounded by molecules or ions called ligands. Coordination chemistry plays a crucial role in various fields due to its impact on color, magnetic properties, and catalysis.

• In the compound \( \mathrm{Mn}_{3}(\mathrm{CO})_{12} \), manganese acts as the central metal with carbonyl groups as ligands.
• Coordination relies on the ability of ligands to donate a pair of electrons to form coordinate covalent bonds with the metal.

Understanding this coordination allows chemists to manipulate the properties of the complexes for practical applications such as industrial catalysis and materials science.

Oxidation State

The oxidation state (or oxidation number) of an element in a compound indicates its degree of oxidation, helping us track electron transfer in reactions. This concept is vital in naming coordination complexes as it impacts their properties significantly.
The oxidation state is determined by assuming all bonds are ionic and using known charges on the ligands and the whole complex.

• In \( \mathrm{Mn}_{3}(\mathrm{CO})_{12} \), the oxidation state of manganese is zero.
• Since carbon monoxide is a neutral ligand, it does not alter the overall charge.

By convention, the oxidation state is often enclosed in parentheses in IUPAC names, as seen in 'trimanganese (0)'. This explicit mention helps avoid misunderstandings about the electron configuration and charge of the complex.

Transition Metals

Transition metals are elements found in the d-block of the periodic table. They have partially filled d-orbitals, which give them unique characteristics such as forming colored compounds, multiple oxidation states, and being good conductors of heat and electricity.
Manganese, the metal in our discussed compound, is a transition metal with versatile chemistry.

• Transition metals like manganese can easily form various compounds with different oxidation states.
• The presence of orbitals allows these metals to form coordinate bonds with a wide range of ligands.

Thus, transition metals are foundational in creating complex coordination compounds, impacting many functional areas such as electronics, medicine, and industrial catalysis.

Ligands

Ligands are atoms or molecules that can donate a pair of electrons to bind to a central metal atom or ion, forming what is known as a coordination complex. This interaction involves the formation of coordinate covalent bonds.

• In \( \mathrm{Mn}_{3}(\mathrm{CO})_{12} \), carbonyl (CO) acts as the ligand.
• It binds to manganese, enabling the formation of the complex by donating electron pairs.

Ligands are crucial because they define the structure and properties of the complex. They can alter the electronic configuration of the metal, and thus affect the stability, reactivity, and functionalities of the resulting coordination complex. Understanding the nature and role of ligands helps in predicting and designing new compounds with desired properties for specific applications.