[janapix]

On reacting sodium borohydride with pyrazole, I get a scorpionate ligand.
I'm not very sure how the reaction proceeds though because I thought borohydrides were just
good for transferring protons. Here, the boron atom links directly to nitrogen.


image link: http://i317.photobucket.com/albums/mm395/MunsterMunster/University%20stuff/ex13d1.png

[orgopete]

If you draw NaBH4, what are the formal charges?

[janapix]

One of the hydrogens on NaBH₄ is a hydride anion... but I've two
rubbishy options for a mechanism from this point:

1. hydride donation to -NH- giving -NH₂-, where nitrogen temporarily contains 10 electrons
and donates a pair to boron, giving both N and B 8 valence electrons.

2. -NH- nitrogen begins by donating a lone pair to BH₄, which then loses its hydride anion. The H^- then proceeds to act as a base, removing H from -NH(BH₃)-

Do these make sense? I get the feeling they're both completely wrong.

note: -NH- refers to the -NH- of pyrazole, as opposed to the -N=