Question

Why doesn't ammonia,NH3 form a di-ammonia compound similar to diborane?(Draw a di ammonia structure).

Answer 1

Nitrogen has 5 electrons in its bonding shells and it would like 8 to be stable. A single nitrogen would be very happy if it were bonded to 3 hydrogen's as this would give it an octet of electrons making it look like Neon. In the N2H6 molecule there would be 9 electrons in the outer shell and this would be an unhappy molecule and so it would break apart to its more stable constituents 2NH3.so ammonia doesn't form a di-ammonia compound similar to diborane.

structure

if you're thinking of H3N-NH3, this compound is highly unlikely to be stable and exist. a single bond is not possible because the molecule would be depleted of 2 electrons and the nitrogen atoms would have a positive charge. the positive charge cannot be delocalized and the charged nitrogen are right next to each other. a molecule with a double bond between the 2 nitrogen is even more unlikely because that would violate the octet rule. i mean each ammonia has one lone pair and these lone pairs are highly repulsive against each other
if you're talking about intermolecular bonds between 2 NH3 yeah it's a dipole-dipole interaction
however ammonia is able to undergo hydrogen bonds which are way stronger that dipole interaction