Electron Deficient Molecules Boron Hydrides Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

7/15/2015 Electron Deficient Molecules Non-transition metal atoms in a molecule or ion which do not have a filled electron shell are referred to as electron deficient. These species often undergo unusual bonding in an attempt to fill their empty shells. The effect is especially noteworthy in elements which form covalent bonds.

The Players N P As Sb O S Se Te B Al Ga In C Si Ge Sn Zn Cd Cu Ag F Cl Br I Ne Ar Kr Xe H

Boron Is Electron Deficient B F F F B F F F B F F F B F F F filled p-orbital of fluorine overlaps empty p-orbital of boron

Boron Is Electron Deficient B H H H hydrogen doesn’t have any filled p-orbitals diborane draw an orbital overlap diagram of diborane B H H H B H H H

Boron Is Electron Deficient diborane B H H H B H H H 97°122° 137 pm 119 pm

Boron Hydrides Closo Structures B 4 H 4 2- B 5 H 5 2- B 6 H 6 2- closo-pentaborane(5)

Boron Hydrides Closo, Nido and Arachno Structures B 6 H 6 2- closo B 5 H 5 4- nido B 4 H 4 6- arachno

7/15/2015

Boron Hydrides Principal Hydrides B 2 H 6 diborane spontaneously inflammable B 4 H 10 tetraborane not spontaneously inflammable B 5 H 9 pentaborane spontaneously inflammable B 5 H 11 pentaborane spontaneously inflammable B 6 H 10 hexaborane-10 62? Stable mp bp air reactivity

B 5 H 9 pentaborane-9

B 10 H 14 decaborane-14

Dicarba-closo-dodecaborane

Boron Hydrides Closo Structures B 4 H 4 2- B 5 H 5 2- B 6 H 6 2-