Question

Identify the incorrect statement.

• A. \( \text{PEt}_3 \) and \( \text{AsPh}_3 \) as ligands can form \( d\pi \)-\( d\pi \) bond with transition metals
• B. The \( \text{N} - \text{N} \) single bond is as strong as the \( \text{P} - \text{P} \) single bond
• C. Nitrogen has unique ability to form \( p\pi \)-\( p\pi \) multiple bonds with nitrogen, carbon and oxygen
• D. Nitrogen cannot form \( d\pi \)-\( p\pi \) bond as other heavier elements of its group

Answer 1

The Correct Option is B

Analysis of each statement:
1. PEt$_3$ and AsPh$_3$ d$\pi$-d$\pi$ bond formation: PEt$_3$ (triethylphosphine) and AsPh$_3$ (triphenylarsine) function as $\pi$-acceptor ligands. The phosphorus or arsenic atom in these ligands possesses vacant d orbitals capable of accepting electron density from the filled d orbitals of transition metals, thereby forming d$\pi$-d$\pi$ backbonds. This statement is accurate.
2. N-N versus P-P single bond strength: The N-N single bond exhibits significantly lower strength compared to the P-P single bond. This reduced strength arises from lone pair repulsion between the nitrogen atoms. Due to the smaller size of nitrogen atoms, their lone pairs are in close proximity, leading to substantial repulsion and weakening the N-N single bond. Phosphorus atoms are larger, resulting in greater separation between their lone pairs, less repulsion, and a stronger P-P bond. Consequently, statement (2) is inaccurate.
3. Nitrogen p$\pi$-p$\pi$ multiple bonding: Nitrogen readily forms p$\pi$-p$\pi$ multiple bonds with itself (N$_2$), carbon (C$\equiv$N, CN), and oxygen (N=O). This is a characteristic feature of nitrogen chemistry and is a correct statement.
4. Nitrogen d$\pi$-p$\pi$ bonding: Nitrogen lacks accessible d orbitals in its valence shell. Therefore, it cannot participate in d$\pi$-p$\pi$ bonding, unlike heavier elements in its group (phosphorus, arsenic, etc.) which possess available d orbitals. This statement is accurate.