CBSE Class 11-science Answered

In diborane four terminal B-H bonds are two centre - two electron bonds. Two bridge B ? H ? B bonds (or banana bonds) are three centre - two electron bonds (shown in figure).

2 boron and 4 terminal hydrogen atoms (H_t) lie in one plane, while the other two bridging hydrogen atoms (H_b) lie in a plane perpendicular to the plane of boron atoms. Again, of the two bridging hydrogen atoms, one H atom lies above the plane and the other lies below the plane. The terminal bonds are regular two-centre two-electron (2c – 2e^–) bonds, while the two bridging (B–H–B) bonds are three-centre two-electron (3c – 2e^–) bonds.