3-6 The Pauling “3-Electron Bond”
43
Figure 3-2: Orbital occupations and electron spins for Pauling “3-electron bonds”.
strength of a “3-electron bond” should be approximately equal to that of a
1-electron bond. If we indicate the spins of the electrons, as in
or
then it is obvious that there can only be one bonding electron, because two
electrons with the same spin cannot form a bond.
For the three electrons of the Pauling “3-electron bond”, a molecular orbital
description of them can also be constructed using the bonding and antibonding
molecular orbitals ab a b
k and
ab
*
a – b
k
. The Pauli exclusion principle
allows only a maximum of two electrons with opposite spins to occupy any
orbital. Therefore for the three electrons of the valence-bond structure A···B , the
molecular orbital configuration
2
* 1
ab
ab
( ) ( )
involves two bonding electrons + one
antibonding electron. For it, the contribution to bonding by one of the two bonding
electrons is cancelled by that of the antibonding electron with the same electron
43
Figure 3-2: Orbital occupations and electron spins for Pauling “3-electron bonds”.
strength of a “3-electron bond” should be approximately equal to that of a
1-electron bond. If we indicate the spins of the electrons, as in
or
then it is obvious that there can only be one bonding electron, because two
electrons with the same spin cannot form a bond.
For the three electrons of the Pauling “3-electron bond”, a molecular orbital
description of them can also be constructed using the bonding and antibonding
molecular orbitals ab a b
k and
ab
*
a – b
k
. The Pauli exclusion principle
allows only a maximum of two electrons with opposite spins to occupy any
orbital. Therefore for the three electrons of the valence-bond structure A···B , the
molecular orbital configuration
2
* 1
ab
ab
( ) ( )
involves two bonding electrons + one
antibonding electron. For it, the contribution to bonding by one of the two bonding
electrons is cancelled by that of the antibonding electron with the same electron