Question:
Explain structures of diborane and boric acid.

Answer:

(a) Diborane B₂H₆ is an electron-deficient compound. B₂H₆ has only 12 electrons - 6 e^-from 6 H atoms and 3 e-each from 2 B atoms. Thus, after combining with 3 H atoms, none of the boron atoms has any electrons left. X-ray diffraction studies have shown the structure of diborane as:

2 boron and 4 terminal hydrogen atoms (Ht) lie in one plane, while the other two bridging hydrogen atoms (Hb) 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.

(b) Boric acid Boric acid has a layered structure. Each planar BO₃ unit is linked to one another through H atoms. The H atoms form a covalent bond with a BO3 unit, while a hydrogen bond is formed with another BO₃unit. In the given figure, the dotted lines represent hydrogen bonds.

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Explain structures of diborane and boric acid.

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Question:
Explain structures of diborane and boric acid.