[azmanam]

I was tutoring someone today, and we were looking back over how atomic orbitals combine to give molecular orbitals.  Later on, we were working through alkene addition reactions and got to the bromination of alkene by molecular bromine.  We got to the bromonium intermediate and were talking about that, and the student asked what the MOs of that bromonium ion would look like.

I didn't have a good answer.  I wondered if it was some kind of 3-center, 2-electron bond similar to diborane complexes, but I couldn't come up with anything definitive.

Anyone have any insight?

[sjb]

Depending on how stringent you mean, I think you may be also to model the HOMO and LUMO very roughly as being similar to those in an oxirane or episulfide. You may get issues with the charge that way, though - would be interested to hear other approaches

[azmanam]

I found this site, that sorta approaches both in terms of MO/AO combining into 2 MOs, and looks at HOMO/LUMO interactions.

http://courses.chem.psu.edu/chem210/mol-gallery/bromonium/bromonium.html

Interesting stuff, this chemistry...