[antimatter101]

Wikipedia explained that half bonds form when there is a deficiency of electrons, and "incomplete bonds" form when a functional group or molecule has insufficient electrons to share so an amount of electrons less than the number of atoms is shared between the group. It gave me an example as diborane (B2H6) but I don't see any "incomplete bonds" in that molecule! And if there is an insufficiency of electrons then that molecule can't form!

[discodermolide]

It's a three centre two electron bond. Have a read here:
http://voh.chem.ucla.edu/vohtar/fall03/classes/30B/pdf/diborane.pdf

[antimatter101]

Is borane really that desperate to make a 3/2 bond? And how does it happen? Instantaneously or slowly?

[discodermolide]

Presumably it is desperate to fulfil its valence shell, if I remember correctly. It's been a long time since I had to deal with the bonding in diborane.
If it happens instantaneously or not I have no idea. But to hazard a guess I would say instantaneously.