Question

Which of the following ligands are capable of linkage isomerism? Explain your answer. $$\mathrm{SCN}^{-}, \mathrm{N}_{3}^{-}, \mathrm{NO}_{2}^{-}, \mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}, \mathrm{OCN}^{-}, \mathrm{I}^{-}$$

Short answer

The ligands capable of linkage isomerism are \(\mathrm{SCN}^{-}\), \(\mathrm{N}_{3}^{-}\), \(\mathrm{NO}_{2}^{-\), and \(\mathrm{OCN}^{-}\) because they have at least two potential donor atoms that can bind to a metal center, allowing for different linkage arrangements.

Step-by-step solution

Identify potential donor atoms

We will look at each ligand and identify the potential donor atoms that can bind to a metal center. 1. \(\mathrm{SCN}^{-}\): Sulfur (S) and Nitrogen (N) are potential donor atoms. 2. \(\mathrm{N}_{3}^{-}\): Nitrogen (N) atoms can be donors, considering both terminal ends. 3. \(\mathrm{NO}_{2}^{-}\): Nitrogen (N) and Oxygen (O) are potential donor atoms. 4. \(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\): Only Nitrogen (N) atoms are potential donor atoms on both ends. 5. \(\mathrm{OCN}^{-}\): Oxygen (O) and Nitrogen (N) are potential donor atoms. 6. \(\mathrm{I}^{-}\): Iodine (I) is the only potential donor atom.

Determine which ligands can exhibit linkage isomerism

For a ligand to exhibit linkage isomerism, it must have at least two potential donor atoms, either of which can bind to a metal center. From Step 1, we can see that the following ligands meet this criterion: 1. \(\mathrm{SCN}^{-}\) 2. \(\mathrm{N}_{3}^{-}\) 3. \(\mathrm{NO}_{2}^{-}\) 4. \(\mathrm{OCN}^{-}\) The other ligands do not meet this criterion, as they only have one potential donor atom each. Therefore, the ligands capable of linkage isomerism are: $$\mathrm{SCN}^{-}, \mathrm{N}_{3}^{-}, \mathrm{NO}_{2}^{-}, \text{ and } \mathrm{OCN}^{-}$$

Key concepts

Coordination Chemistry

Coordination chemistry is an intriguing area of inorganic chemistry that deals with complexes formed between metal ions and molecules or ions that can donate electrons, known as ligands. These complexes are vital not only in laboratory synthesis but also in many biological systems.

In coordination complexes, the metal ion is the central element surrounded by ligands, which are bound to it through coordinate covalent bonds. This occurs when a ligand donates a pair of electrons to the metal ion, creating a unique bond known as a coordination bond. The resulting structures are often colorful and exhibit a range of chemical and physical properties that are exploited in various technological applications, such as in catalysts and medicines.

Donor Atoms

A donor atom is an atom within a ligand that possesses at least one lone pair of electrons which it can donate to form a bond with a metal ion in a coordination complex. These atoms are usually nonmetals like nitrogen, oxygen, sulfur, or halogens such as chlorine and iodine.

Importance of Donor Atoms in Coordination Chemistry

Donor atoms are essential because they determine the binding mode and the overall geometry of the coordination complex. The nature and number of donor atoms can influence the properties of the complex, such as reactivity and stability. The electronic characteristics of donor atoms also contribute to the ligand field, affecting the color and magnetic properties of the complex.

Ligands

Ligands play a significant role in the formation of coordination compounds. They are ions or neutral molecules that have one or more donor atoms capable of donating an electron pair to form a coordinate bond with a metal ion.

Ligands are classified based on their denticity, which refers to the number of donor atoms they contain. Monodentate ligands have only one donor atom, whereas polydentate ligands, also known as chelates, have multiple donor sites that can bind to a single metal ion, forming a loop and a more stable complex.

Inorganic Chemistry

Inorganic chemistry is a branch of chemistry that focuses on the study of inorganic compounds, which typically do not contain carbon-hydrogen (C-H) bonds, in contrast to organic compounds. Within this broad field, coordination chemistry is a key topic, involving the study of metals and their complexes with ligands.

Inorganic chemistry covers a variety of topics including the behavior of elements, their compounds, the principles that govern their combination and reaction mechanisms, as well as the applications of these materials in technology, medicine, and environmental science. It is a foundational subject that helps us understand the behavior of all chemical elements and their inorganic compounds.