Addendum Chapter 3
53
9 M. Green and J.W. Linnett, J. Chem. Soc., 4959 (1960).
10 J.W. Linnett, Sci. Progress (Oxford), 60, 1 (1972).
11 R.F. Hudson, Angewandte. Chem. (Int. Ed.), 12, 36 (1973).
12 F. Bernardi, N.D. Epiotis, W. Cherry, W.B. Schlegel, M.-H. Whangbo and S. Wolfe, J.
Amer. Chem. Soc. 98, 469 (1976).
13 N.C. Baird, J. Chem. Educ., 54, 291 (1977).
14 R. Steudel, Angewandte. Chem. (Int. Ed.), 14, 655 (1975); and references therein.
15 J.C. Slater, Quantum Theory of Molecules and Solids, (McGraw-Hill), (1973) Vol. 1,
p. 111, 190 and references therein.
16 R.D. Harcourt, Aust. J. Chem. 31, 199 (1978).
17 F. Bernardi, W. Cherry, S. Shaik and N.D. Epiotis, J. Amer. Chem. Soc., 100, 1352
(1978).
18 A.R. Gregory and V. Malatesta, J. Org. Chem. 45, 122 (1980)
19 C.A. Coulson, Proc. Roy. Soc. A, 109, 413 (1939).
20 R.D. Harcourt, J. Amer. Chem. Soc., 100, 8060 (1978); 101, 5456 (1979).
Addendum Chapter 3
1) As is discussed in Ref. 21 for example, valence-bond structures of the types
A B and A B for two bonding electrons + one antibonding electron,
are frequently used to represent a Pauling “3-electron bond”. In each of these
structures, the top dot is the antibonding electron. The basic theory is that for a
diatomic system, with overlapping a and b atomic orbitals, two bonding
electrons + one antibonding electron is proportional to two electrons with
parallel spins occupying the a and b atomic orbital, + one AB bonding electron
with opposed spin, regardless with how the wavefunction for the two bonding
electrons is constructed, i.e the valence bond identity A B A B A B
pertains.
Although the Green-Linnett valence bond symbolisms are rarely used, each of
the VB structures, A
B, A B
O
x
x
and
O
A B
O x
shows more clearly than do
A B, A Band A B that the Pauling 3-electron bond involves two
“non-bonding” electrons with parallel spins (which are net antibonding when
the atomic orbital overlap integral S ab is included), and one bonding electron
whose spin is opposed to that of the non-bonding electrons. The antibonding
electron is available for external bonding to either another atom or another
three-electron bond structure.
2) When the Heitler-London wavefunction a(1)b(2) + b(1)a(2) is used as the
wavefunction for the A-B electron-pair bond, and an electron is added to the
antibonding molecular orbital φ* ab = a – kb, the Pauling “3-electron bond”
identity,
53
9 M. Green and J.W. Linnett, J. Chem. Soc., 4959 (1960).
10 J.W. Linnett, Sci. Progress (Oxford), 60, 1 (1972).
11 R.F. Hudson, Angewandte. Chem. (Int. Ed.), 12, 36 (1973).
12 F. Bernardi, N.D. Epiotis, W. Cherry, W.B. Schlegel, M.-H. Whangbo and S. Wolfe, J.
Amer. Chem. Soc. 98, 469 (1976).
13 N.C. Baird, J. Chem. Educ., 54, 291 (1977).
14 R. Steudel, Angewandte. Chem. (Int. Ed.), 14, 655 (1975); and references therein.
15 J.C. Slater, Quantum Theory of Molecules and Solids, (McGraw-Hill), (1973) Vol. 1,
p. 111, 190 and references therein.
16 R.D. Harcourt, Aust. J. Chem. 31, 199 (1978).
17 F. Bernardi, W. Cherry, S. Shaik and N.D. Epiotis, J. Amer. Chem. Soc., 100, 1352
(1978).
18 A.R. Gregory and V. Malatesta, J. Org. Chem. 45, 122 (1980)
19 C.A. Coulson, Proc. Roy. Soc. A, 109, 413 (1939).
20 R.D. Harcourt, J. Amer. Chem. Soc., 100, 8060 (1978); 101, 5456 (1979).
Addendum Chapter 3
1) As is discussed in Ref. 21 for example, valence-bond structures of the types
A B and A B for two bonding electrons + one antibonding electron,
are frequently used to represent a Pauling “3-electron bond”. In each of these
structures, the top dot is the antibonding electron. The basic theory is that for a
diatomic system, with overlapping a and b atomic orbitals, two bonding
electrons + one antibonding electron is proportional to two electrons with
parallel spins occupying the a and b atomic orbital, + one AB bonding electron
with opposed spin, regardless with how the wavefunction for the two bonding
electrons is constructed, i.e the valence bond identity A B A B A B
pertains.
Although the Green-Linnett valence bond symbolisms are rarely used, each of
the VB structures, A
B, A B
O
x
x
and
O
A B
O x
shows more clearly than do
A B, A Band A B that the Pauling 3-electron bond involves two
“non-bonding” electrons with parallel spins (which are net antibonding when
the atomic orbital overlap integral S ab is included), and one bonding electron
whose spin is opposed to that of the non-bonding electrons. The antibonding
electron is available for external bonding to either another atom or another
three-electron bond structure.
2) When the Heitler-London wavefunction a(1)b(2) + b(1)a(2) is used as the
wavefunction for the A-B electron-pair bond, and an electron is added to the
antibonding molecular orbital φ* ab = a – kb, the Pauling “3-electron bond”
identity,