Question

Given below are two statements:
Statement I: \(N(CH_3)_3\) and \(P(CH_3)_3\) can act as ligands to form transition metal complexes.
Statement II: As \(N\) and \(P\) are from the same group, the nature of bonding of \(N(CH_3)_3\) and \(P(CH_3)_3\) is always the same with transition metals.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Statement I is incorrect but Statement II is correct
• B. Both Statement I and Statement II are correct
• C. Statement I is correct but Statement II is incorrect
• D. Both Statement I and Statement II are incorrect

Answer 1

The Correct Option is C

To determine the correctness of the statements provided regarding the ligands \(N(CH_3)_3\) (trimethylamine) and \(P(CH_3)_3\) (trimethylphosphine), let's evaluate each statement individually:

1. Statement I: \(N(CH_3)_3\) and \(P(CH_3)_3\) can act as ligands to form transition metal complexes.
   • In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. Ligands like \(N(CH_3)_3\) and \(P(CH_3)_3\) are known as donor ligands where nitrogen and phosphorus donate their lone pair of electrons to the metal center.
   • Both trimethylamine (\(N(CH_3)_3\)) and trimethylphosphine (\(P(CH_3)_3\)) can indeed act as ligands. Nitrogen and phosphorus both have lone pairs that they can use to coordinate with transition metals, forming complexes.
   • Therefore, Statement I is correct.
2. Statement II: As \(N\) and \(P\) are from the same group, the nature of bonding of \(N(CH_3)_3\) and \(P(CH_3)_3\) is always the same with transition metals.
   • Although nitrogen and phosphorus are in the same group of the periodic table and share some chemical similarities, they are different in terms of their size and their ability to back-bond with metals.
   • Nitrogen's smaller size and higher electronegativity compared to phosphorus often result in different bonding characteristics and complex stabilities. For example, phosphorus can sometimes use its d-orbitals for back-bonding, something nitrogen does not have access to due to its lack of low-energy d-orbitals.
   • Hence, the assertion that the bonding nature is always the same between these two ligands is incorrect.
   • Therefore, Statement II is incorrect.

Based on the analysis, the most appropriate answer is: Statement I is correct but Statement II is incorrect.

Answer 2

To correctly analyze the given statements and determine their accuracy, let's understand the basis of each statement:

Statement I: \(N(CH_3)_3\) and \(P(CH_3)_3\) can act as ligands to form transition metal complexes.

This statement is about the ability of trimethylamine (\(N(CH_3)_3\)) and trimethylphosphine (\(P(CH_3)_3\)) to act as ligands. Both compounds contain a lone pair that can be donated to a metal center, which is a key characteristic of ligands. Therefore, both can indeed form coordination complexes with transition metals. This makes Statement I correct.

Statement II: As \(N\) and \(P\) are from the same group, the nature of bonding of \(N(CH_3)_3\) and \(P(CH_3)_3\) is always the same with transition metals.

Although nitrogen and phosphorus belong to the same group (Group 15) in the periodic table, they differ significantly in their chemical behavior as ligands:

• Nitrogen: Trimethylamine (\(N(CH_3)_3\)) typically acts as a σ-donor, providing its lone pair to form a sigma bond with metal centers.
• Phosphorus: Trimethylphosphine (\(P(CH_3)_3\)), however, can function not only as a σ-donor but also as a π-acceptor due to its ability to engage in back-bonding with metal d-orbitals. This phenomenon significantly influences the character of the complexes it forms.

Because the coordination behavior of nitrogen and phosphorus compounds can differ, the statement that the nature of bonding is "always the same" is incorrect.

Thus, the correct analysis is: Statement I is correct but Statement II is incorrect.