Question

Which of the following is not a borane?
(A) ${{B}_{2}}{{H}_{6}}$
(B) ${{B}_{3}}{{H}_{6}}$
(C) ${{B}_{4}}{{H}_{10}}$
(D) none of these

Answer 1

The boranes that were prepared by Stock had the general composition ${{B}_{n}}{{H}_{n~+\text{ }4}}~$ and ${{B}_{n}}{{H}_{n~+\text{ }6}}$ , but more complex species, both neutral and negative (anionic), are known. The ability of boron to form bonds in addition to normal covalent bonds leads to the formation of complex polyhedral boranes.

Complete step by step solution:
Boranes are chemical compounds of boron and hydrogen. The boranes comprise a large group of compounds with the generic formula of ${{B}_{x}}{{H}_{y}}$ . These compounds do not occur in nature. Many of the boranes readily oxidize on contact with air, some violently. The parent member $B{{H}_{3}}$ is called borane, is known only in the gaseous state, and dimerizes to form diborane, ${{B}_{2}}{{H}_{6}}$ .
The larger boranes all consist of boron clusters that are polyhedral, some of which exist as isomers.
The most important boranes are diborane ${{B}_{2}}{{H}_{6}}$, pentaborane ${{B}_{5}}{{H}_{9}}$, and decaborane ${{B}_{10}}{{H}_{14}}$ .
Out of the given options, ${{B}_{3}}{{H}_{6}}$ is not a borane.
${{B}_{2}}{{H}_{6}}$ is a diborane, formed by dimerisation of unstable $B{{H}_{3}}$. ${{B}_{4}}{{H}_{10}}$ is a tetraborane.

Hence the correct option is the B option.

Note: The nomenclature of borane involve following characteristic structural prefixes: (1) closo- deltahedrons of n boron atoms; (2) nido- non closed structures in which the ${{B}_{n}}$ cluster occupies n corners of an (n + 1)-cornered polyhedron—i.e., a closo-polyhedron with one missing vertex; (3) arachno-, clusters that are even more open, with boron atoms occupying n contiguous corners of an (n + 2)-cornered polyhedron—i.e., a closo-polyhedron with two missing vertices; (4) hypho-, the most open clusters, with boron atoms occupying n corners of an (n + 3)-cornered closo-polyhedron; and (5) klado-, n vertices of an n + 4-vertex closo-polyhedron occupied by n boron atoms.