Diborane

A compound capable of making the sea change in its creation, would be diborane, B₂H₆, with weird chemical properties but having immense potential to be of use in a plethora of industrial and scientific applications. Diborane is an extremely reactive, colorless gas with repulsive smells, similar to sickly sweetness. Its unusual bonding and high reactivity have attracted the attention of chemists since its synthesis.

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This Story also Contains

1. Diborane: Structure and Properties
2. Types and Aspects of Diborane
3. Relevance and Applications of Diborane
4. Some Solved Examples
5. Summary

In organic chemistry, for example, it represents one important reagent for hydroboration, which allows complex molecules to be fabricated like those used in pharmaceuticals and agrochemicals. In the high-tech industry related to electronics, diborane is used for chemical vapor deposition to make the boron-doped silicon used when fabricating semiconductors and many other electronic devices.

Diborane: Structure and Properties

Diborane is a boron hydride chemical compound with the molecular formula B₂H₆. It has an exceedingly weird structure wherein two boron atoms are held substantially by three-center, two-electron bonds; both of the boron atoms are four-bonded: two terminal B-H bonds and two B-H-B bridging bonds. This unusual bonding arrangement gives rise to characteristic properties of diborane. It is highly reactive and acts like a reducing agent. The structure of the diborane determines its chemical behavior and thus its reactivity.

The simplest boron hydride known is diborane. B₂H₆ is prepared by the following methods:

• Laboratory Method: In the laboratory, it is prepared by the reaction of sodium borohydride with iodine in a high boiling polyether solvent(CH₃OCH₂CH₂)₂O.$2{\mathrm{NaBH}}_4+{\mathrm{I}}_2\stackrel{\text{Polyether}}{\to }{\mathrm{B}}_2{\mathrm{H}}_6+2\mathrm{NaI}+{\mathrm{H}}_2$
• Industrial Method: $2{\mathrm{BF}}_3+6\mathrm{LiH}\stackrel{450\mathrm{K}}{\to }{\mathrm{B}}_2{\mathrm{H}}_6+\mathrm{LiF}$
• From Boron Halides:$4{\mathrm{BX}}_3+3{\mathrm{LiAlH}}_4\to 2{\mathrm{B}}_2{\mathrm{II}}_6+3\mathrm{LiX}+3{\mathrm{AlX}}_3$
• When boron halides and excess hydrogen undergo a reaction by passing silent electric discharge at low pressure, B₂H₆ is formed.

Types and Aspects of Diborane

The most widely employed application of diborane is in the hydroboration reactions whereby it adds across the carbon-carbon double bond to give organoboranes. These organoboranes then convert into many useful compounds, examples of which are their reduction to alcohols, amines, and halides. Another application of diborane is in CVD for the creation of high-purity thin films containing boron species. On the other hand, pentaborane and decaborane, the derivatives of the diborane series, exist to manifest a wide range of properties and applications as BH derivatives do.

Relevance and Applications of Diborane

The applications of diborane extend far beyond a laboratory to be sure. It finds a place as a reagent in organic chemistry for the synthesis of complex molecules, like pharmaceuticals and agrochemicals. This makes it a very strong tool in the armamentarium of organic synthesis since it can selectively reduce compounds. On the other hand, semiconductor industries also make use of diborane in chemical vapor deposition processes, during which, with its help, resulting boron-doped films of silicon are formed; it is quite essential to be used in the manufacturing of electronic devices. Moreover, much attention is paid to diborane as a rocket fuel due to the large content of energy in its molecule. However, its reactivity and toxicity do not give any chance for practical application. As for academic disciplines, the study of diborane allows the development of advanced bonding theories and reaction mechanisms; therefore, research into this field is made in inorganic chemistry courses.

Recommended topic video on (Diborane)

Some Solved Examples

Example 1

Question:

How many isomeric disubstituted borazine B₃N₃H₄X₂ are possible?

Solution:

Disubstituted borazine has 4 isomers: Ortho, meta-1, meta-2, and para isomers.

Therefore, the correct number of isomeric disubstituted borazine is 4. Hence, the correct option is (2).

Example 2

Question:

In B₂H₆, which of the following statements is correct?

1) There is a direct boron-boron bond.

2) The B-H bonds are ionic.

3) It is isostructural to C₂H₆.

4) Boron atoms are linked through hydrogen bridges.

Solution:

In B₂H₆, the structure includes three-center two-electron bonds, also known as banana bonds. There are two types of B-H bonds:

$(B-H_t)$: Normal covalent bond (2c-2e bond)

$(B-H_b)$: Bond between three atoms $(B-H_b-B)$ (3c-2e bond)

B₂H₆ has two 3c-2e bonds made by bridged hydrogens between the two borons.

Therefore, the correct option is (4): Boron atoms are linked through hydrogen bridges.

Example 3

Question:

The number of 2-center-2-electron and 3-center-2-electron bonds in B₂H₆ respectively are:

1) 4 and 2

2) 2 and 4

3) 2 and 2

4) 2 and 1

Solution:

B₂H₆, or diborane, has a structure that includes three-center two-electron bonds (banana bonds). There are two types of B-H bonds in diborane:

$(B-H_t)$: Normal covalent bond (2c-2e bond)

$(B-H_b)$: Bond between three atoms $(B-H_b-B)$ (3c-2e bond)

Diborane has four 2-center-2-electron bonds and two 3-center-2-electron bonds.

Therefore, the correct option is (1): 4 and 2.

Summary

Amongst such compounds, as an extraordinary structure with wide applications in the range of hydroboration reactions to CVD processes, stands that of diborane in organic synthesis and materials science. Indeed, this proves to be very challenging since it is highly reactive and toxic. Still, it is the potential that keeps researchers on track through research and innovation. The understanding of diborane will not only improve our knowledge about boron chemistry but also give way to new technological perspectives.