Question

The soft Lewis base(s) is(are)

• A. \( I^- \)
• B. CO
• C. \( H^- \)
• D. \( \text{CH}_3\text{NC} \)

Hint:

Soft bases like \( H^- \) donate electrons easily due to their low charge density and ease of interaction with soft acids.

Answer 1

The Correct Option is A, B, C, D

To identify the soft Lewis bases among the given options, we need to understand the concept of Lewis acidity and basicity as well as the classification of bases as hard or soft. According to Pearson's Hard and Soft Acids and Bases (HSAB) principle, soft bases easily pair with soft acids due to their polarizability and charge distribution.

Let's evaluate each option:

• \( I^- \): Iodide ion is a large, polarizable ion making it a soft base. It has electron pairs that can easily be shared with a soft acid.
• $CO$: Carbon monoxide is a soft base because the carbon has lone pair electrons in its half-filled orbital, which are in a low oxidation state. Its ability to form back-bonding also contributes to its softness.
• \( H^- \): The hydride ion can be considered a soft base due to its high polarizability and its ability to donate electrons easily under certain conditions.
• \(\text{CH}_3\text{NC}\): Methyl isocyanide has a lone pair on carbon that makes it act as a soft donor due to the availability of electrons for donation.

All options \( I^- \), $CO$, \( H^- \), and \(\text{CH}_3\text{NC}\) qualify as soft Lewis bases due to their polarizability and electron-donating capabilities, which are characteristic features of soft bases.

Therefore, the correct answer encompasses all the given options.