Higher Boron Hydrides Flashcards

Flashcards based on lecture notes about Higher Boron Hydrides.

What is the general formula for Higher Boron Hydrides?

BpHp+q

What type of bonds are found in Higher Boron Hydrides?

Delocalised bonds including BHB 3c 2e bonds and closed BBB bonds.

How is a closed BBB bond formed?

When 3 sp3 hybrid orbitals on 3 boron atoms point towards the center of an equilateral triangle.

What is detailed electron pair counting used for in the context of Boron Hydrides?

To explain the bonding in simple molecules by accounting for valence electrons in B-H terminal, B-H-B bridge, and B-B bonds.

What is the total number of valence electrons in B4H10?

22 (11 pairs)

What is the total number of valence electrons in B5H11?

26 (13 pairs)

Why might a molecular orbital treatment be more appropriate for larger boron hydride molecules?

Because as molecules get larger, localised models require more resonance structures.

According to Lipscomb, which boron atoms carry more negative charge in B5H9?

Apical boron atoms carry more negative charge than basal boron atoms.

In [B6H6]2-, what is assumed about each BH unit?

Each BH unit consists of an sp hybrid and a conventional 2c 2e bond between the B and H.

What are the three classes of boranes mentioned?

Closo, Nido, and Arachno.

According to Wade’s Rules, what determines the stability and classification of boranes?

The number of framework pairs compared to the number of vertices in the molecule.

In the formula [(BH)pHq]c-, what does 'p' represent?

The number of B-H units or vertices.

In the formula [(BH)pHq]c-, how do you calculate the total number of framework electrons?

2p + q + c

According to Wade's rules, how many framework pairs does a closo borane have?

p+1

According to Wade's rules, how many framework pairs does a nido borane have?

p+2

According to Wade's rules, how many framework pairs does an arachno borane have?

p+3

What is the number of vertices (p) for [B6H6]2-?

6