Q. Simple molecular orbital description?

we can give a simple molecular orbital description of bonding in B₂H₆ as follows. Each boron atom is sp³ hybrid giving four sp³ hybrid orbitals, one of which is vacant and the other three are singly filled. Two of the sp³ hybrid orbitals on each boron atom are used to form terminal B-H bonds with singly filled 1s orbital of hydrogen. Two BH, units are then brought together so that all six atoms are coplanar. Then one singly filled sp³ hybrid orbital on one B atom and one vacant sp³  hybrid orbital on the other B atom overlap with the singly filled 1s orbital on  hydrogen atom to ford a bonding orbital shaped like a banana and covering all three  atoms, viz, R, H and R. Similarly the other bonding orbital iz :!so formed.

This orbital binding three atoms contains only two electrons; the bonding between the bridging H atom and the B atom is thus only about half as strong as in the conventional two-centre two-electron terminal bonds. The B2H6 molecule contains two such three-centre electron pair bonds. Due to repulsion between the two H nuclei  the delocalised orbitals are bent away from each other giving it the banana' shape.