[vhpk]

Hi all,
I wanna ask about HSAB. One problem I met today is to categorize the hard and soft bases and acids. One question is about NO⁺, the answer is soft base. However I got quite confused since as you know, NO+ will use the electron pair on N to donate to the metal ion like the C use its lone pair to donate to metal ion, the lone pair here accommodates on N which is an electronegative element and small --> high charge density --> hard base. Is my argument correct?
Plz help me with this. Thank you

[AWK]

NO+ will use the electron pair on N to donate to the metal ion

This statement is true for neutral NO

[vhpk]

NO+ will use the electron pair on N to donate to the metal ion

This statement is true for neutral NO

Thank you, but could you elaborate more? As for me, no matter what electron is used, it's on either N or O, so anyway, it should be hard base, shouldn't it?

[lancenti]

It's true that a hard base typically has a high negative charge density, or is a small atom. That's why AWK says that it's true for Neutral NO.

Now consider NO⁺. Is it going to want to behave as a base? What about its negative charge density? Once you answer those two questions it should become clear.

As a tidbit, NO⁺ is quite likely a hard acid.