BASF - 5-2-2004 at 08:20
Borazine is known as the "inorganic" benzene although it is not aromatic.
The hydrogens at the boronns are more easily substituted than the carbons on the benzene-ring.
Although the density is much lower for a boron-compound, the high heat of formation of N2 and B2O3 still has to be considered, in my opinion.
My suggestion in terms of achieving a higher density would be to get a pentafluorosulfonyl-group on the borons(reactive with nucleophiles) and get a
fuel-group(methyl- / thio- or amino- (hydrogen-bonding 
etc..) on the
aza-position(s).
chemoleo - 5-2-2004 at 09:08
Slightly related to your quest is this:
http://www.sciencemadness.org/talk/viewthread.php?tid=1244